Cream the butter and sugar together until light and fluffy.
Add the eggs, one at a time, with the crème fraiche and beat the mixture well.
Mix the cocoa powder and baking powder with the flour until well mixed. Use a metal spoon to fold the flour into the batter.
Line a muffin tin with paper cases and divide the mixture between them.
Preheat the oven to 180 C / 350 F / 160 FAN / Gas 4.
Bake for about 20 minutes until the cupcakes are well risen.
Leave in the tin for a few minutes then transfer to a wire rack to cool completely.
To make the icing, stir the cocoa powder and icing sugar together and mix with the butter and a tablespoon of the milk. Stir in the remaining milk if required, so that the icing is a soft consistency.
Use a spatula to fill an icing bag fitted with a large star nozzle. Pipe the icing around the outside edge towards the centre in a spiral. This will give a 'nest' effect for the mini eggs.
Top the icing with 3 eggs on each cake before serving.