Preheat the oven to 180°C (356°F).
In a bowl, mix the eggs and sugar together.
Add the milk and melted butter, and mix well.
Sift the cake flour, cocoa powder, and baking powder into the mixture and stir to combine.
Add chocolate chips and gently fold them in.
Divide the batter evenly into muffin molds.
Bake at 180°C (356°F) for 20 minutes.