Preheat the oven to 180'C.
Place cupcake cases into silicone or tin moulds.
Whisk together the butter and the sugar until light and creamy. Add one egg at a time and combine well. Sift the flour, the cocoa powder and the baking powder into the mixture and gently fold together. Spoon the mixture into the cupcake cakes, transfer to the oven and bake for 12 to 14 minutes.
Remove from the oven and leave to cool.
Melt the milk chocolate over a bain-marie.
Sift the icing sugar into a large bowl, add the butter and beat until pale and fluffy. Stir in the melted chocolate, combine well and then transfer the icing to a piping bag with a star nozzle.
Once the cake are completely cooled, pipe on the icing and finish with a dusting of cocoa powder to finish.
«Allow the melted chocolate to cool a little before adding to the butter. This will prevent the butter from melting.»