To make the sponges, add the soft butter and sugar to a bowl, and use a hand mixer to cream them together.
Add the eggs one by one, mixing well after each addition.
Sift in the flour and cocoa powder, then add the vanilla extract and use a spatula to mix.
Line a 6-hole muffin tray with paper cases, and divide the batter evenly.
Bake in the preheated oven at 200 degrees Celsius (390 Fahrenheit) for 20 minutes until the sponges are firm and a skewer inserted in the middle comes out clean.
Leave to cool completely.
To make the frosting, add the soft butter to a food processor together with the sifted icing sugar, vanilla extract, milk, and blitz to get a smooth paste - alternatively use a hand mixer to get the frosting.
Add the food colouring and mix again.
Add the frosting to a piping bag and decorate each cupcake, then make it spooky by using edible eyes or any other edible decoration.