Preheat the oven to 180°C.
Add eggs and sugar to a bowl and mix well.
Add melted butter and milk, and mix together.
Sift in flour, cocoa powder, and baking powder, then mix.
Add chocolate chips and knead the dough.
Divide the batter into the muffin cups.
Bake in the oven at 180°C for 20 minutes.