Sweet Sourdough Starter:

1. Mix 40ml of oat milk with 40g flour, 10g sugar, and 30g active sourdough starter.
2. Cover and leave in a warm spot overnight or until doubled in size.

Tangzhong:

1. In a small pot, whisk 140ml oat milk with 35g flour.
2. Warm on medium heat, whisking until thickened and reaching about 150°F/65°C.
3. Transfer to a bowl, cover with clingfilm, touching the Tangzhong to prevent a skin from forming, and let it cool to room temperature.

Main Dough:

1. Combine all ingredients except butter and salt. Allow a 30-minute autolyse.
2. Add salt, knead for 5-10 minutes, then slowly add half the room temperature butter.
3. Knead for 15-25 minutes until gluten develops and the dough passes the windowpane test.
4. Let the dough rest covered for about 3 hours until doubled in size.
5. Store the dough in the fridge overnight.

Laminating the Dough:

1. Flatten a cold butter stick between parchment paper to an 8×8 square.
2. Roll out the dough to a 16″ x 24″ rectangle.
3. Place the butter in the middle or your rolled out dough, fold like an envelope, and roll out to seal in the butter.
4. Turn by 90 degrees, repeat the folding and rolling out.
5. Wrap into plastic wrap and leave to rest in the fridge for 20-30 minutes.
6. Repeat the folding and rolling process twice, resting in the fridge between each cycle.

Preparing the Filling:

1. Melt 2 tbsp butter for brushing onto the rolled-out dough.
2. For dark chocolate filling: Roughly chop dark chocolate.
3. For cinnamon sugar filling: Mix 3 tbsp sugar with 1 tsp cinnamon.

Last Rolling Out and Filling:

1. Roll out the dough thinly to about 1/16” into a rectangle.
2. Brush with melted butter and sprinkle with the chosen filling.
3. Roll up the dough, cover, and chill for at least 20 minutes or overnight.

Cut and Add to Loaf Tins:

1. Grease 2 loaf tins or line with parchment.
2. Cut dough rolls into 3 equal pieces each and add to tins, cut side facing up, so you see the pretty spirals.
3. Brush with melted butter, sprinkle with brown sugar and cinnamon.
4. Let rise covered outside of the fridge for an hour.

Baking:

1. Preheat the oven to 375°F/190°C.
2. Bake for 25-30 minutes, then cover with foil and bake 10-15 minutes longer.
3. Cool on a rack. Dust with icing sugar if desired.
4. Enjoy your Sourdough Brioche Feuilletee with jam or butter!