Put the flour and cocoa powder in a bowl and mix.
Add sugar, yeast, and salt.
Pour in warm milk and eggs, and knead the dough.
Add butter and knead until the dough becomes smooth.
Let the dough rise for the first fermentation.
Divide the dough and shape it into round balls.
Place them on a pan and let them rise for the second fermentation.
Bake in a preheated oven at 180°C for 15 minutes.