Preheat the oven to 180'C.
Place the Guinness in a pan and reduce by two thirds and allow to cool.
Whisk together the butter and the sugar. When light and fluffy in texture slowly add the eggs one by one. When all of the eggs are incorporated, slowly sift the self raising flour, baking powder and the cocoa into the butter mixture. Finally add the reduced Guinness. Fold the mixture very gently with a spatula. Ensure all of the flour is mixed in well.
Pour the mixture into a piping bag. Pipe the mix into the cupcake cases 3/4 full.
Bake in the oven for 12 minutes. Remove from the oven and allow to cool before decorating.
Crush the walnuts and mix with the mascapone, gingerbread spice and the sugar.
When the cakes are cool, scoop out a small section from the top of the cakes and fill it with the gingerbread mix.
Sieve the icing sugar.
Beat the butter and the icing sugar together until it is light and fluffy. Add the cream cheese and combine well.
Place the icing in a piping bag with a star nozzle. Begin to ice the cakes by starting on the outside and working your way into the centre.
«Cool the Guinness down completely before adding it to the cake mixture to prevent it from splitting.»