Mix bread flour, cocoa powder, sugar, and salt in a bowl.
Add warm milk and yeast, then mix well.
Add egg and butter, and knead into a dough.
Let the dough rise for the first fermentation.
Divide the dough and shape into balls.
Add chocolate chips into the dough and form shapes.
Place the dough on a baking pan for the second fermentation.
Bake in a preheated oven at 180°C for 15 minutes.