First take the sugar and butter and mix well.
Now in the butter and sugar mix the warm milk till the mixture is smooth enough.
Now sift in the flour,unsweetened cocoa powder and baking powder.
Now take cupcake liners or ramekins and butter them so that the cake comes out smoothly.
Fill the ramekins or the cupcake liners and then put a piece and half of the chocolate bar in the middle and just dab the mixture on top of the chocolate.
Preheat oven at 180 degrees.
Now keep the ramekins in the oven for about 8-9 minutes.