In a large mixing bowl, whisk together 500 grams of bread flour, 50 grams of cocoa powder, and 50 grams of sugar until well combined.

Gradually stir in 350 grams of sourdough starter and 300 grams of lukewarm water into the dry ingredients until a shaggy, wet dough forms.

Transfer the shaggy dough onto a floured surface and knead for about 10 minutes until smooth and elastic.

Gently flatten the dough and sprinkle 10 grams of salt and 100 grams of dark chocolate chips over the surface, folding to incorporate.

Place the dough in a lightly greased bowl and cover; allow it to rise in a warm environment for 4-6 hours.

Once risen, punch down the dough, shape it into a loaf, and place it in a greased 9x5-inch loaf pan; let it rise for 2-3 hours.

Preheat your oven to 220°C (428°F) about 30 minutes before the second rise is complete.

Bake the loaf in the preheated oven for 30-35 minutes until the crust is firm and sounds hollow when tapped.

Allow the loaf to cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.