Pre-heat the over to 180 degrees/Fan 160 degrees/Gas 4. Put muffin cases into a 12-hole muffin tin.

Mix the butter and caster sugar together until fully incorporated. Then add the eggs, one at a time until they are both mixed in.

Add the vanilla, flour and cocoa powder to the sugar and egg mix then mix until the mixture is fully incorporated. Add in a handful of chocolate chips and stir them in by hand. Using an ice cream scoop, fill each cupcake case about three quarters full.

Bake in the pre-heated oven for about 20-25 minutes until risen and golden brown. Lift paper cases out of the tin and cool cakes on a wire rack until completely cold before icing.

To make the butter icing, beat the butter until its light and fluffy. Then add in the vanilla and the icing sugar a little bit at a time until its fully incorporated.

Using piping bag with a star nozzle, pipe the buttercream on to the top of each cupcake until they are all covered. Then take a mini cookie and one to the top of each cupcake.