Preparation of Sourdough Starter

1. Combine equal parts of flour and water in a clean glass or ceramic container until smooth.
2. Cover loosely and let sit at room temperature for 24 hours.

Step-by-Step Starter Preparation

1. Daily, discard half the starter and replenish with fresh flour and water. Stir well.
2. Continue for 5-7 days until the starter doubles in size and develops a sour aroma.
3. Watch for bubbles on the surface, indicating active fermentation.

Combining Ingredients

1. In a large bowl, whisk bread flour, all-purpose flour, cocoa powder, salt, and sugar.
2. Make a well and add water and active starter. Mix to form a shaggy dough.
3. Fold in optional ingredients if using.
4. Adjust with extra water or flour to achieve a slightly sticky, manageable dough.

First Fermentation (Bulk Fermentation)

1. Place dough in a lightly oiled bowl. Cover and let ferment at room temperature for 4-6 hours, folding dough occasionally.

Shaping and Final Proofing

1. Shape the dough on a floured surface into a boule or batard.
2. Place in a floured proofing basket, cover, and let rise until light and airy, about 1-2 hours.

Baking

1. Preheat oven to 450°F (230°C). Place a baking stone or heavy baking sheet inside.
2. Create steam by adding hot water to a shallow pan in the oven.
3. Bake at 450°F for 20 minutes, then reduce to 400°F and bake for another 25-30 minutes.
4. Bread is done when internal temperature reaches 200-205°F or sounds hollow when tapped.