1. 1. Combine Starter and Water: In a large mixing bowl, gently whisk together the active sourdough starter and the warm water until the starter is mostly dissolved. The mixture should look milky and slightly frothy.

2. 2. Mix Dry Ingredients: In a separate bowl, combine the bread flour, all-purpose flour, unsweetened cocoa powder, granulated sugar, and fine sea salt. Whisk them together thoroughly to ensure even distribution of the cocoa and sugar.

3. 3. Form the Dough: Add the dry ingredient mixture to the wet starter mixture. Use a sturdy spoon or your hands to mix until all the flour is hydrated and a shaggy dough forms. Cover the bowl with a damp cloth or plastic wrap and let it rest for 30 minutes.

4. 4. Incorporate Chocolate Chips and Begin Folding: After the rest, sprinkle the dark chocolate chips over the dough. Gently fold the dough over itself several times to distribute the chocolate chips. Then, perform your first set of stretch and folds: grab a portion of the dough, stretch it upwards, and fold it over to the center. Rotate the bowl and repeat this process 3-4 times until the dough feels slightly tighter. Cover and let rest for 30 minutes. Repeat this stretch and fold process three more times, with 30-minute rests in between each set.

5. 5. Bulk Fermentation: After the final set of folds, cover the bowl and let the dough bulk ferment at room temperature for 3-5 hours, or until it has visibly increased in volume by about 30-50% and appears bubbly.

6. 6. Shape the Loaf: Gently turn the dough out onto a lightly floured surface. Shape the dough into a round or oval loaf. If using a banneton, place the shaped dough seam-side up in a lightly floured banneton. If not, place it seam-side down on a piece of parchment paper.

7. 7. Proofing: Cover the shaped dough loosely with plastic wrap or a damp towel and let it proof at room temperature for 1-2 hours, or until it feels light and airy. Alternatively, you can cold proof it in the refrigerator overnight (8-12 hours).

8. 8. Bake the Loaf: Preheat your oven to 450 F (230 C) with a Dutch oven inside for at least 30 minutes. Carefully remove the hot Dutch oven. Gently transfer the dough into the Dutch oven. Score the top of the dough with a sharp knife or razor blade. Cover the Dutch oven and bake for 30 minutes. Remove the lid and continue baking for another 10-15 minutes, or until the crust is deeply browned and the internal temperature reaches 200-210 F (93-99 C).

9. 9. Cool Completely: Carefully remove the loaf from the Dutch oven and transfer it to a wire rack. Let it cool completely for at least 1-2 hours before slicing. This step is crucial for the crumb to set properly and for the flavors to fully develop.