1) Preheat the oven to 180 degrees C/Gas Mark 4. Line standard cupcake tins with 18 cupcake liners.
2) In the bowl of an electric mixer fitted with the paddle attachment, cream butter and sugar until light and smooth. Add the eggs, 1 at a time, beating until each is smooth, scraping down the sides of the bowl if needed. Add the vanilla.
3) Sift the cocoa, flour, baking powder, bicarbonate of soda, and salt in a large bowl. In the creamed bowl, alternate the leftover ingredients beginning and ending with dry ingredients. Stir in the sauerkraut. Fill the cupcake liners 2/3 full. Bake until the cupcake springs back when touched, about 35 minutes. Transfer the pans to wire racks to cool completely before removing the cupcakes.
For the beer icing:
In the bowl of an electric mixer fitted with the paddle attachment, mix the softened butter with half the icing sugar. Add the cocoa, salt, and roughly 1/3 of the beer. Beat until smooth. Alternate adding the remaining sugar with the remaining beer and beat until fluffy.
Ice the cooled cupcakes with beer icing.
This recipe was provided by professional chefs and has been scaled down from a bulk recipe provided by a restaurant. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.