Method for the cakes:
Melt the butter in a saucepan over a low heat, add the chocolate powder and stir until melted.
In a large bowl beat together the sugar, eggs and yoghurt. Add the melted chocolate and stir until well mixed.
Sieve the flour and fold into the chocolate mixture.
Spoon mixture into 12 muffin cases.
Bake for 15-20 minutes at 180 deg C (160 deg C fan ovens) Gas Mark4, until risen and springy to touch, leave to cool.
For the icing:
Melt the couverture over a pan of barely simmering water.
In a large bowl, beat the butter until soft, then sieve in the icing sugar, add the milk and melted couverture. Beat together until combined and smooth.
Spread over the fairy cakes and decorate.
