Ultra-Moist Protein Chocolate Cake with Sourdough

Tired of choosing between a dry high-protein dessert and a satisfyingly moist chocolate cake? I created a better option! This cake has double the protein of an average slice, uses sourdough discard for max moisture, and has about 100 fewer calories than a classic version. We pair it with a rich, creamy, high-protein cashew chocolate mousse frosting that is easy to digest. It’s the perfect balance of flavor, texture, and nutrition. Try a slice—You won’t look back!

 

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• Why You’ll Love This
• The Ingredients
• Substitutions
• Equipment Used
• How to Make this
• How To Store
• FAQ
• Other Recipes You Might Enjoy

Why You’ll Love This 

TL;DR

• Protein-Powered: Enjoy a moist, fluffy chocolate cake with double the protein of your average slice.
• Sourdough Magic: The sourdough discard ensures a super moist crumb and adds a lovely tang to balance the sweetness.
• High-Fiber, Lower Calorie Frosting: The rich, creamy Cashew Protein Chocolate Mousse frosting is dairy-free, high in fiber and protein, and is much easier to digest than traditional buttercream.
• Effortless Baking: The cake batter comes together quickly in just one bowl with no fancy equipment needed.
• Make-Ahead Friendly: The cake stores beautifully in the fridge for up to 4 days, tasting great from day one to day four.

The Cake That Lets You Have It All

Have you ever tried to decide between a high-protein recipe that will come out dry and unsatisfying and that super moist and fluffy chocolate cake which has none of the benefits but is just oh-so-good?

Yup, me too. Been there, done that and decided to create a better option for all of us. Because we deserve a sourdough chocolate cake that is just as good for us as it tastes.

Well…I mean, it does have sugar and white flour, but look, it also has double the protein of your average chocolate cake, features sourdough discard for moisture, and has about 100 calories less per slice.

And after all we are talking cake. Fluffy, moist and rich chocolate cake with a super creamy frosting!

Try and resist eating a slice right after baking, I dare you!

How does this recipe do it? Let me explain.

The Magic Of Sourdough And Protein

There is a magical thing that happens when you combine sourdough and protein powder: The sourdoughs ability to hold onto moisture counters any potential dryness from the protein powder, balancing out the downsides you usually get in high protein recipes. You can see this in action in all my protein sourdough recipes.

In this chocolate cake (as in many sweet recipes), the sourdough also adds a really pleasant tang—not making it taste sour, but rather balancing the sweetness, giving it another dimension, even with a hint of maltiness, leading to an utterly irresistible slice of heaven. To up the protein even further, I also included fat free Greek yoghurt instead of milk or buttermilk. Fat free for fluffier results, not so much to save calories. Though it does that too.

A Dairy-Free Frosting That Is Good For You

While I mentioned frosting above: Yup, this recipe comes with a rich and creamy chocolate frosting too. And now you might think I’ll give you one of those Greek yoghurt-protein powder mixed things and call it protein cream. But nope, not my style!
See, while I’m not a big fan of the classic buttercream, let alone cream cheese frostings (they do make me feel slightly queasy. Maybe the lactose and incredibly high fat?), I still want a fluffy, creamy and deeply chocolatey filling and covering for my cake. I mean, you don’t bake a layered cake every day, right? (Though I swear I want to!) So you need a proper one to satisfy the craving!

In my search for an easier digestible, higher protein and all around better for me option, I thought of my Protein Cashew Chocolate Mousse and boy was that a good idea!
It has no added sugar, aside from the bit in the dark chocolate.

I realize, since the cake isn’t vegan, this might feel like a slightly odd choice and sure, you can absolutely use your favorite chocolate buttercream on this dreamy protein chocolate cake, but I’m fairly sure after you tried the cashew chocolate mousse, you won’t want to.

It’s super simple to make in a blender, comes together in minutes, is high in fiber and protein, very low in lactose, making it a great option for anyone sensitive to dairy, as I’m using plant milk (tiny bit of it in the whey protein, but feel free to use a nice tasting vegan option) and deeply chocolatey, thanks to three different chocolate additions.

Easy One Bowl Sourdough Discard Cake

Talking about simple: The cake batter comes together in one bowl, just using a hand mixer or even whisk. Not even butter and sugar creaming is needed, neither smoothing of the top, since it becomes very runny by adding some freshly brewed coffee to it.

I modified this recipe using Nora’s incredible vegan chocolate cake as my starting point. Her trick to add boiling water activates the cocoa powder flavor and keeps the cake moist. Pure genius if you ask me.
I’ve added even more punch to the chocolate by using freshly brewed coffee (the cake won’t taste like coffee, no worries) instead of just water.

Now, since her recipe says (correctly) it’s “The Best” vegan chocolate cake, I should possibly claim that mine is the best sourdough protein chocolate cake. But right now, from all I can see, it’s the only one out there. And I’d rather let you be the judge of the quality.
So after trying this, I’d love to hear what you think!

Ingredient Notes

As usual, just the most relevant ones that I feel need notes. The full list including amounts is in the recipe card.

Chocolate Protein Cake Batter

• All-Purpose Flour – This is the best flour for cake, as it gives you a tender and fluffy result.
• Sugar – Granulated or caster sugar work best to give you the volume and lightness.
• Cocoa Powder – Non-Dutch is best for intense chocolate flavor and it’s slight acidity. In the original recipe the acidity also helped to activate the baking soda, but with my additions that wouldn’t be a concern.
• Personally I adore Valrhona for its incredibly intense flavor, but any unsweetened cocoa powder will be fine.
• Just don’t use anything labelled “Drinking chocolate”, as these powders are usually sweetened and often have other ingredients (like milk powder and cornstarch) added, that would throw off the balance here.
• Baking Soda & Powder – With sourdough discard some might wonder (as I did) why I would add it, with the sourdough rise and all. But for one, since I’m not leaving it to ferment overnight, as I don’t want much gluten development for a tender cake, the sourdough won’t get around to adding much air to the batter. However the discard does add a little acidity. And while I do appreciate a slight tang and love how it balances the sweetness in chocolate cake, the baking soda neutralises a bit of it, to keep it gentle and not overpowering. Plus of course the combo of soda and baking powder gives a lovely rise.
• Whey Protein Powder – Whey concentrate to be exact, as it still has a bit of fat and lactose (minimal) helping with the softness and moisture of the cake. Ideally chocolate flavored, since I replaced part of the cocoa from the original recipe with it.
• Fat Free Greek Yoghurt – Why am I choosing fat free? Because it is there to replace milk as liquid and a full fat version would make this cake much heavier. So you get lower calories and higher protein with this swap.
  Also: This will not make the cake taste sour in the slightest. And just as the sourdough, the acidity from the yoghurt tenderizes and counters any potential drying protein powder effect.
• Coconut Oil – Oil gives cakes an incredible moisture and I find coconut just goes perfect with chocolate.
• Dark chocolate – I’m only using a tiny bit, to emphasize the chocolate flavor. For me, in the first try, it just felt a little too…gentle. But then, I usually like really dark and fudgy brownies. So if you are a fan of the more milk chocolate candy-like flavor in chocolate cake, feel free to leave it out and add back ¼ cup sugar instead.
• Sourdough Discard – Mine was fed about 3 days before making the cake. You don’t want it unfed for too long, to control the acidity. I’d say stored in the fridge anything up to 5 days is fine.
• If your discard has been in the fridge for more than 5 days, I highly recommend feeding it 1:1:1 and waiting about 6 hours before using it, to ensure the right acidity and balance.
• Coffee – This might be the most unusual ingredient in this cake but trust me it really works. The coffee flavor amps up the chocolate and the hot liquid gives moisture. I use fresh americano, but instant coffee will be fine.

Cashew Protein Chocolate Frosting

• Cashews – These are the base for this frosting, as they blend up super creamy and delicious.
• Plant Milk – I used unsweetened soy milk this time. Oat milk works great too. Both are full fat and pretty creamy, which is what we want in a frosting.
• Dates – They are the sweetener for this fluffy chocolate cream and contribute a lovely hint of caramel flavor plus a little fiber.
• Chocolate – I like a dark chocolate with around 70% cocoa. But if you have one with higher content, feel free to use that. There is plenty of creaminess to balance it.
• Whey Protein – Mine is whey concentrate with chocolate flavor, because…well, we are making a chocolate frosting, so might as well throw as much chocolate as possible at it, right?
• Cocoa Powder – The third contributor of chocolate flavor. I’ve made this without, and it was pleasant, but I feel the addition just gives the cream an intense chocolate punch. Again, I love Valrhona, but any unsweetened cocoa powder will work. It adds some thickening qualities and stability to the frosting.
• Instant Espresso – This, just as the Amaretto, are both entirely optional, but really dial up the chocolate flavor. If you are making this for kids, leave them out.

substitutions

While I give a whole list of substitutions here, each of them alters the texture and flavor ever so slightly. So I would advise to only pick one or two, not all of them, as that might lead to rather wild results.

As an example: While you can swap the eggs and greek yoghurt for the vegan version, I would then not necessarily want to add gluten free flour too, as it can have quite an impact on texture. Does that make sense?

Chocolate Protein Cake Batter

• Flour – While I haven’t tried this myself, as we don’t get it here, I read that King Arthur Gluten free flour is a great substitute for all purpose. But with the sourdough discard adding some gluten, I would still only advise this swap if you were gluten sensitive, not celiac.
• You could however replace about 1/3 of the AP flour with fine whole wheat flour. Your cake may not be as soft but will gain a lovely nutty flavor.
• Eggs – If you’d like to replace the two eggs, add 60ml/1/4 cup plant milk and 40g flour to get very similar results in texture.
• Sugar – If you’d like to make a sugar free cake, Xylitol will work well as replacement.
• Whey Protein Powder – While I feel whey concentrate works best in the context of this rich and fluffy sourdough chocolate cake, you could use Casein and add two tablespoons more hot water to balance its higher liquid absorption.
• If you’d like to use a vegan powder, I would firmly vote for the Plant Protein Superblend from MyProtein (not sponsored or affiliated, but the only vegan protein so far I really enjoyed to use in my baking) and reduce the water from the brewed coffee by two tablespoons, to compensate for its lower liquid absorption.

Note:

If you happen to use any other protein powders, I’d love to hear from you about how they worked, as it helps me with recommendations in my recipes.

• If you’d like to bake this cake entirely without protein, you can simply replace it with the same amount of flour and it’ll work wonderfully.
• Sourdough Discard – You can of course use active sourdough starter. If you want to skip the sourdough entirely, replace it with 120g flour (1 cup) and 105ml more hot water.
• Coconut Oil – Any neutral oil like canola or avocado will work. I often use olive oil instead and adore the flavor. For once I would not use butter, as oil is giving you a decidedly moister result.
• Fat Free Greek Yoghurt – A vegan version will work, so will full fat Greek yoghurt. Your cake will be even richer.
• Dark Chocolate – You could use milk chocolate for a sweeter flavor or leave it out. Your cake will have a slightly less intense chocolate flavor but still be utterly delicious.
• Coffee – I love using freshly brewed americano, but instant coffee works just fine. If you don’t want the caffeine, but keep the flavor, decaf is a great option. Or just use hot water.

Cashew Protein Chocolate Frosting

• Cashews – If you don’t have a high speed blender, you can use cashew butter instead with a few important caveats:
  Make sure the cashew butter you are using has no added oil or other ingredients. A hint of salt is fine.
• Cashew butter is usually made from roasted cashews, leading to a more intense nutty flavor.
• Use half the amount of cashew butter in volume that I’ve given below (that’s 1/3 cup).
• Add liquid gradually, until you get the right consistency. Cashew butter reacts different than raw cashews, so you might have to experiment a little.
• Mix with a hand mixer or stand mixer, to get the same fluffiness I achieve by blending in a high speed blender.
• Dates – You can use about 2 tbsp or so of honey or maple syrup instead
• Plant Milk – You can of course use any kind of milk. I happen to be lactose intolerant which mainly shows up when using anything non-fermented, hence only having plant milk at home.
• Chocolate – Vegan chocolate works well. Most dark versions are incidentally vegan anyway. White chocolate could work, if you want to mix things up, but I’d reduce the plant milk by about 2-4 tbsp as it sets softer.
• Protein Powder – Replace with cocoa powder and 2 tsp cornstarch, to achieve a similar creamy result.
• Cocoa powder – Ok look, I have not tried this, but if you’d like to make a creamy vanilla frosting instead of chocolate, consider using some malted milk powder instead of the cocoa. I bet it would be stunning!
• Instant Coffee and Amaretto – Both are entirely optional. But if you’d like to keep the gentle almond flavor without using amaretto, add ¼- ½ tsp almond extract for a very similar effect.

Weigh Your Ingredients

Being from Europe, for me, weighing ingredients has always been the standard. When I spotted the American cup system, I thought, “Well, that’s kinda handy!” until I noticed how wildly different the weight vs. volume can be, especially for ingredients like flour.

You can easily add an extra 30g of flour (1/4cup) by simply dragging your measuring cup through the bag instead of gently spooning and leveling it. This leads to wildly different results in baking.

And when it comes to sourdough discard, volume measurements are especially tricky. Just think about freshly fed starter versus discard that’s been in the fridge for a few days—the volume can change drastically, so you most certainly want to weigh yours!

Another benefit of weighing your ingredients? You only have your mixing bowl and a spoon to wash, not a mountain of measuring cups! Just use the Tare function on your scale and weigh ingredients right into your bowl.

Equipment Used

Chocolate Cake Batter

• Bowls – I used one large bowl to mix the batter and a smaller bowl for the dry ingredients. You could just add the dry ingredients on top of the wet and give them a quick stir, if you want to only use one bowl.
• Whisk – You can of course use a hand mixer or stand mixer like the KitchenAid, but I decided to make this by hand, as it’s easy enough even with my arthritis.
• Cake Pans – 8 x 2 Inch deep

Cashew Protein Frosting

• High Speed Blender – I love using my Nutribullet for this, but any high speed blender will work. If you don’t have one, don’t despair and check my note on cashews in the substitutions.
• Offset Spatula – Makes icing a cake so much easier!

Glass bowl

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whisk

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Nutribullet

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How to Make this

Protein Chocolate Cake Batter

Preparations

• Pre-heat your oven to 350°F/175°C
• Line the cake pans with baking parchment (watch the video to see how to do this neatly.)

• Don’t grease the sides. This will help the batter to “climb” up and rise nicely.

• Weigh your mixing bowl and write the weight down. This means, you can then weigh it again to get the weight of the batter, divide it by 2 and get the exact amount to add to each cake pan. That way you’ll have very evenly baked and sized layers.

Melt Your Chocolate

• Add coconut oil and chocolate either to a microwave safe bowl or a double boiler and gently melt.
• Allow to come to room temperature while you mix your remaining ingredients.

Mix The Dry Ingredients

In your large mixing bowl whisk flour, sugar, cocoa powder, baking powder, baking soda and salt together.

Add The Wet Ingredients

Add the sourdough discard, eggs, Greek yoghurt and vanilla extract and cooled, melted chocolate with the coconut oil and mix until just combined

Pour Over Coffee

• Brew some coffee freshly (either Americano or instant coffee). Don’t do this ahead of time, you want it still hot, so it activates the full cocoa flavor and keeps the dough super moist. This works very similar to the Yudane method I used in my Fluffy Sweet Potato Rolls, in gelatinizing part of the flours starches, giving you a super soft interior.
• Whisk until everything comes together in a pourable batter. This will be very runny; don’t be alarmed. It’s working as intended.

Divide Between The Cake Pans

• Now, since you wrote down the weight of your mixing bowl (you did, right?), weigh your bowl with the batter again. Subtract it’s weight from the bowl. Then pour half of it into one of the prepared baking pans and the other half into the second.
• In case you forgot: The batter weighs about 1420g, so you pour about 700g into each of the cake pans. That leaves room for the 20g that might just stick to the sides of the bowl. Of course you could scrape them out, but I think they make a great bakers snack.
• Of course you could just eyeball it (I did so many times). Just make sure to then test them separately for doneness, as one might need longer than the other.

Bake Your Protein Chocolate Cake Layers

Bake for 35 to 40 minutes, or until a toothpick inserted into the center comes out clean.

Allow to cool for about 30 minutes in the pans, then turn out onto a cooling rack until completely cooled.

Make The Protein Chocolate Mousse Frosting

You can make this the day before (or even 2 days) and store it in the fridge to firm up.

Soak The Cashews

Boil a kettle and pour the hot water over your raw cashews. Leave for about 20-30 minutes. Alternatively you can soak them in cold water overnight.

Melt The Chocolate

Break the dark chocolate into rough pieces and add to a microwave safe bowl (or use a double boiler) with a bit of the plant milk. Heat in short bursts, stirring in between, until the chocolate is melted.

Blend Your Ingredients

• Drain your cashews.
• Now, simply add everything to your blender, starting with the cashews, followed by the protein powder, cocoa, melted chocolate mix, dates, salt, instant coffee, and Amaretto if using, finishing with the plant milk. This order (mostly) prevents the pesky protein powder sticking to the blades problem.
• Blend until you have a super smooth, fluffy and creamy frosting. Give it a taste and see if you like the sweetness. I find it’s plenty sweet from the dates and protein powder, but if you have a particularly sweet tooth, feel free to drizzle in some honey or add a bit of sugar.

• Allow to cool and firm up about 2 hours in the fridge. You can even make this up to 2 days in advance and let it set fully before frosting your cake.

Assemble Your Super Moist Chocolate Cake

• If you want a perfectly flat top (I don’t mind mine being a bit domed), you could flatten your cake disks by slicing off the top with a sharp knife or use the method I learned from my Grandfather, by running a sharp knife just around the top corner, then grab some sewing thread, lay it into the groove you just cut, cross over itself at the front of the cake and pull. You can see this best in the video.
• And you have a perfectly smooth top!

• Pick the one that looks best for the top.
• Start by spreading about 1/3 of the cashew chocolate mousse on the bottom cake layer. I like doing this on a rotating cake platter, but frankly, just a normal large plate works fine. A palette knife is super helpful here to get it even.

• Gently place the second cake layer on top. Spread a thin layer of your frosting all over the cake, to catch any crumbs. This is the crumb coating, mean to give you a nice and clean finish.
• Finish by spreading the remaining chocolate coating over your cake. It doesn’t have to be perfect!

• Decorate if you like. A bit of whipped cream/cashew cream looks nice, so do a few raspberries or some seasonal decoration.
• But all in all this is one of those super simple cakes that saves you in case of an urgent chocolate craving!
• And now the most important point:
  Enjoy! It’s fabulous with a hot cup of coffee or just a glass of cold milk.

Watch The Video

How To Store

This cake is best stored in a cake transport box in the fridge for up to 4 days. Since it has no cream, the frosting tastes exactly the same on day 4 as it did on day 1.

The cake’s high moisture content, thanks to the sourdough and hot coffee, also means it stays incredibly moist and tender for the full 4 days.

So this Protein Powder Chocolate Cake is fabulous to make ahead.

Now I’d love to hear from you in the comments!

Have you tried this? Did you enjoy it?
What other recipes would you like to see?

And if you enjoyed this recipe, please consider rating, sharing, or leaving a comment – your feedback truly helps my blog grow!

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