Preheat oven to 190°C (374 °F )
Mix the eggs with the sugar, cocoa, milk and warm melted butter in a mixing bowl.
Add flour and mix. Add the milk chocolate pieces and whisk.
Then add the baking powder and baking soda and mix well.
Pour the batter into a piping bag or freezer bag, make a hole at the bottom and fill your muffin cups almost to the top.
Place in the oven for 25-30 minutes.
Check for doneness with a skewer inserted into the center of a muffin. It should come out dry.
They're even better when eaten warm to enjoy the melt-in-the-mouth texture of the chocolate pieces.