Day 1:

1. Sourdough Feeding
2. Two days before making the donuts, feed your sourdough starter to have at least ½ cup of active starter. Follow my sourdough starter’s guidelines for feeding if unsure.

Cider and Yeast

1. Start by boiling 2 cups of apple cider down to ½ cup. Allow it to cool until lukewarm.
2. In a bowl, combine the lukewarm apple cider and active dry yeast. Allow it to bubble up for about 10 minutes. If it doesn’t bubble, your yeast may not be active anymore.

Preparation

1. Pre-mix the protein powder with the liquid ingredients (eggs, sourdough starter, vanilla extract, Greek yogurt, and salt) to create a smooth mixture. You can use a blender or whisk by hand.

Making the Dough

1. In a stand mixer or a large bowl, combine flour, ground cinnamon, ground nutmeg, melted and cooled butter, granulated sugar, light brown sugar, and the protein-egg mix.
2. Mix with a spoon until you have a rough mixture, then knead using a stand mixer or by hand until you have a smooth, elastic dough that sticks to the bottom of the bowl but comes away from the sides. Adjust with more flour if it’s too soft or a bit of milk or water if it’s too dry.
3. Perform the windowpane test to check if the gluten is properly activated.
4. Grease a bowl with oil, form the dough into a ball, and place it in the greased bowl. Cover and let it rest.

Resting and Stretching

1. Let the dough rest and ferment for about 2 hours at room temperature. Optionally, perform a few stretch and folds every 30 minutes within the first 2 hours.
2. After the initial rest, place the dough in the refrigerator to rest overnight.

Shaping the Donuts

1. Two hours before frying the donuts, take the dough out of the fridge and let it come to room temperature.
2. Flour a work surface, take the dough out of the bowl, and add more flour if necessary to prevent sticking.
3. Roll out the dough to a thickness of about ½ inch.
4. Use a 2-inch round cookie cutter or a glass to cut out the donuts. Place them on a parchment-lined baking sheet with space in between.
5. Combine and roll out the leftover dough, cutting out more donuts until all the dough is used.
6. Cover the donuts with plastic wrap and let them rest for 45 minutes while you heat the frying oil.

Heating the Oil

1. In a large, heavy-bottomed pot or cast-iron pot, add enough oil (2-3 inches) for frying. Heat the oil to 350°F (175°C) using a thermometer or by observing the bubbles on a wooden spoon handle.
2. Preparing Cinnamon Sugar and Plum Curd
3. Mix sugar and cinnamon on a large plate for rolling the donuts.
4. If using Spiced Plum Curd, fill a piping bag with a long, thin nozzle or use a freezer bag. Fill the bag with the curd.

Frying the Donuts

1. Take one donut as a test. Fry it for about 45 seconds on each side until it turns deep golden brown. Ensure it’s cooked all the way through and fluffy inside.
2. Adjust the oil temperature if necessary. It’s important not to let the oil get too hot.
3. Once you’ve reached the right temperature, fry 4-5 donuts at a time, flipping them until they are deep golden brown and puffed up.
4. Remove the donuts with a slotted spoon and roll them in the cinnamon sugar while still hot. Place them on a parchment-lined tray.
5. Keep the fried donuts warm in the oven at the lowest temperature while you fry the rest.

Optional Filling with Spiced Plum Curd

1. For filling, poke a hole in each donut about halfway through using a round wooden spoon handle or a food-safe tool.
2. Use the piping bag with Spiced Plum Curd to fill the donuts until they are filled to the top.
3. Place the filled donuts upright on the tray, filled side up.
4. Enjoy your delicious Sourdough Apple Cider Donuts with Spiced Plum Curd!