For the icing, beat the butter, icing sugar and blended cocoa together. Spread 3 tablespoons over one cake. Then either:
1) Spread the remaining icing over the other cake
2) Place the remaining icing in a piping bag with a star nozzle and pipe a border around the iced cake. Use the remaining icing to spread over the other cake.
Sandwich both cake together.
Decorate with Chocolate Buttons, rubbing them between your fingers to make them shine. Enjoy