Place the butter and sugar into a bowl or mixer and mix until they are of a creamy, light consistency. 

Next add the eggs, one at a time, ensuring to mix well between each addition to incorporate as much air as possible. Once all the eggs are combined add the peppermint extract, and stir well. 

Finally, sift the flour and cocoa powder into the mixture and fold in using a figure of eight action, ensuring you scrape the bottom. 

Place the cake batter into the cupcake cases, filling them until they are 2/3 full. Place on the middle shelf of the oven and cook for 12-15 minutes or until springy to the touch. 

Once the cakes are cooked leave them to cool on a wire rack. 

Meanwhile, for the icing place the softened butter into a bowl and sift the icing sugar in gradually, mixing well between each addition. If the icing is too thick you can add a small amount of milk to loosen it to a pipable consistency. Finally add the Peppermint extract and a small amount of gel food colouring, until the icing is a mint green colour. 

Prepare an icing bag with a nozzle of your choice (I used a Wilton 2D), and fill with your icing. 

Once the cakes are completely cool pipe in your desired design. I started from the outside of each cupcake and worked my way inward and upwards. Finally, place two Aero pieces on top. 

Happy Baking!