Melt the butter in a casserole.
Whip the eggs in to a mousse, than add the sugar, melted butter and your choice of flavor.
Mix the flour and the baking powder in a bowl and mix it in the batter. Make sure the batter is smooth and not to compact. Add milk if it is to compact.
Let the batter in the fridge for 1 hour.
Preheat the oven at 210 degrees Celsius.
Butter and flour the shell-shape baking form and fill the forms to 3/4
Place the cakes in the middle of the oven, and when the cakes have a nice bump in the middle, lower the heat to 180 degrees Celsius. The baking time takes approximately 10 minutes in total. Take out the Madeleines when surface is golden brown.