recipe for cupcakes and buttercream icing is the same as the previous vanilla cupcakes but all you need to do is, cut the top off the cupcakes, fill in with butter cream. cut the sliced top in half and place the half slices of cake on top to resemble butterfly wings.
mary berry made a different version - orange butterfly cakes. see recipe here.
http://www.bbc.co.uk/food/recipes/orange_butterfly_cakes_82059