Line a cupcake tray with cupcakes liners and preheat the oven to 375 degrees. Melt the butter.

In a bowl combine the flour, cocoa, baking powder, sugar, chocolate chips and marshmallows. In a large mixer whisk the egg, milk and melted butter. Slowly add the flour mixture until completely mixed. This will form a stiff batter. Divide the batter evenly into the 12 cupcake liners. Bake for 20 minutes. Remove from oven and cool on a cooling rack.