Pre-heat oven to 180ºC/350ºF/Gas Mark 4. Place the Baking Cases into a muffin tin.
Cream together the butter and sugar until it changes colour (It gets much lighter).
Tip – Crack the egg into a cup rather than into the bowl in case any shell goes in.
Traditionally you would gradually beat in the eggs before folding in the dry mixture, but with this mixture, you can add it all in after creaming.
Sift the cocoa powder and add the other remaining cake ingredients to the bowl and mix until just combined.
Tip – Use an ice cream scoop for filling the cases, that way they are much easier for kids to fill the cake cases and also you can a measured amount meaning that they all cook evenly.
Place spoonfuls of the mixture into the baking cases and bake for 15 – 20 minutes until well risen and firm to the touch. Remove from oven, leave to cool on a cooling rack.
Take a sharp knife and cut a circle out of the top of each cake at an angle about 1cm (½ inch) from the edge. Cut each circle in half and set aside.
To make the butter icing, place the butter in a bowl and beat until soft. Sift and mix in the icing sugar and cocoa powder and then add enough milk make the icing fluffy and spreadable.
Tip: Place a towel around the top of the mixer to prevent the icing sugar flying everywhere.
Sift and beat the cocoa powder into the icing and fill your piping bag. Pipe the icing into the hole in the cakes.
Tip: A piping bag with a BIG star nozzle makes piping super easy for children.
Place the two halves of cake on top to resemble butterfly wings. Dust the top of each cake lightly with the sieved icing sugar or decorate (we used wafer flowers).