Double Chocolate Espresso Sourdough

1. Whisk cocoa powder and espresso/coffee together. Let sit for 2–3 minutes.
2. Add sourdough starter, sugar (or maple syrup), and vanilla extract. Stir to combine.
3. Add bread flour (and espresso powder if using). Mix until just combined. Rest the dough for 30 minutes.
4. Add salt to the dough.
5. Perform bulk fermentation for 4–6 hours, including 3–4 stretch & folds. Add the dark chocolate chips during the second stretch & fold. After bulk fermentation, shape the dough, rest for 15 minutes, then perform a final shape.
6. Cold proof the shaped dough for 8–14 hours.
7. Bake the sourdough: Preheat oven to 475°F. Bake covered for 25 minutes. Then, reduce oven temperature to 450°F and bake uncovered for an additional 20 minutes, or until the internal temperature reaches 208–210°F.