In a large mixing bowl, whisk together the warm coffee and Dutch cocoa powder until smooth. Let sit for 1–2 minutes.

Add the active sourdough starter, warm water, brown sugar, vanilla, and salt. Stir until well combined.

Stir in the bread flour until you have a shaggy, sticky dough and no dry spots remain.

Cover with a damp towel and let the dough rest for 30–45 minutes.

With wet hands, perform a set of stretch and folds by pulling the edge of the dough up and folding it over the center. Turn the bowl and repeat for all four sides. Do 3–4 sets of stretch and folds, spacing them 30–45 minutes apart.

Cover the bowl and let the dough rise in a warm spot until doubled in size (about 4–6 hours, depending on your kitchen temperature).

Turn the dough out onto a lightly floured surface. Sprinkle the chocolate chips over the dough and gently fold them in. Shape the dough into a round or oval loaf, pulling the surface tight.

Place the shaped loaf seam-side up in a floured banneton basket or a small bowl lined with a floured towel. Cover and refrigerate overnight (8–12 hours).

Lay a piece of parchment paper over the loaf and invert onto your work surface. Score the top of the dough with a sharp knife or razor blade. Lift the dough using the parchment and place it in a preheated Dutch oven.

Bake at 450°F (232°C), lid on, for 35–40 minutes, until set and golden brown. Cool on a wire rack before slicing.