Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4, and grease and line two 8" cake tins that are at least 2" deep
To make the chocolate sponge, mix the butter and caster sugar together in a large bowl, ideally using an electric mixer for best results
Add the eggs and milk, and whisk until fully incorporated
Add the self raising flour, cocoa powder and baking powder and gently whisk in until you can't see any flour anymore
Divide the mixture between the two tins, you can use scales for accuracy
Bake them for 35 minutes, check they are done by inserting a skewer or cocktail stick in the middle and if it comes out clean the cake is done, then remove from the tins and leave them to cool on a cooling rack
Level the sponges if they have domed at all with a knife or a cake leveller
For the buttercream mix together the icing sugar, butter, cocoa powder, milk and peppermint extract either by hand or with an electric whisk until smooth, if the buttercream is too stiff then you can add a little more milk
Place the first sponge on your cake stand or cake board, and pipe or spread some buttercream onto it, then add the second sponge on top
Smooth more buttercream around the sides in a thin layer, ideally using an angled paletteknife, and stick the mint Matchmakers all around the cake
Tie the green ribbon around the cake in a nice bow, or use double sided tape
Pipe or spread more buttercream over the top of the cake in a generous layer, then placed the Aero Bubbles on top neatly in rows, or in a big pile instead
Store leftovers in an airtight container in a cool place and eat within 3 days