The secret ingredient is sepia ink ! You can also use charcoal to make these black buns !
Put flour + salt + sugar in a bowl. Make a hole and put the yeast in it. Add the egg + milk + water and finally the sepia ink. Knead during about 10 minutes at speed 3.
Add the softened butter gradually. Form a ball with the dough and leave to rest during 1H30 at room temperature with a cloth on top.
Degas the dough and form little balls (120gr each). Put the balls on a baking sheet and leave to rest during 1h30 at room temperature.
Brush the buns with egg white and sprinkle with sesame seeds.
Bake 15 min at 390°F (200°C).
There you are !