Put the Mini Reese's Peanut Butter Cups in the freezer for at least 1 hour
Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4, and line a cupcake tin with cupcake cases
To make the sponge, mix together the butter, peanut butter and golden caster sugar, ideally using an electric mixer for 2-3 minutes
Then add the eggs and milk and whisk them in
Then gently whisk in the self raising flour
Divide the mixture between the cupcake cases. Place three of the frozen Mini Reese's Peanut Butter Cups on top of the batter of each cupcake and push them in slightly
Bake them for 20-25 minutes or until a skewer inserted in the cupcakes comes out clean. Leave to cool completely
To make the buttercream, mix together the butter and peanut butter until smooth. Add the icing sugar, cocoa powder and milk. Mix again until smooth. This is best done with an electric mixer. If the buttercream is too stiff, you can add a little more milk
Put the buttercream in a piping bag fitted with a nozzle and pipe it onto the cupcakes, or spread on with a spoon
Slightly warm the peanut butter in the microwave for 15-20 seconds, or until it is a pourable texture. Drizzle it over the buttercream either using a piping bag or a spoon
Put half of a Reese's Peanut Butter Cup onto each cupcake
Store in an airtight container in a cool place, eat leftovers within 3 days