Method
Put the butter into a bowl and beat until creamy. Gradually beat in the icing sugar, a few spoons at a time to prevent it flying everywhere.
Add the milk at various times to help mix well. Finally mix in the cocoa and then beat the whole mixture well.
Add more milk if too firm.To make up the cake, cut the tops off each cake to make even surface.
Keep the top bits and break them into a bowl in small chunks. Put one half standing upright on a cake board or plate, spread the surface with icing (hiding sweets in the cake at this point if using) and then put on the other cake upside-down so that you now have an egg shape with a flat top.
Mix the top pieces of cake with some icing and then mould a top onto the cake to make the egg dome.
Then cover the whole egg cake with the rest of the icing and smooth over the surface.
Tie a ribbon round the middle of the cake and leave in a cool place until ready to serve. Cut long thin slices.