From Feast, by Nigella Lawson
Cake:
1 cup Guinness
1/2 cup plus 2 tablespoons butter
1/2 cup cocoa
2 cups superfine sugar
3/4 cup sour cream
2 eggs
1 tablespoon vanilla extract
2 cups all-purpose flour
2 1/2 teaspoons baking soda
Frosting:
8 ounces cream cheese
1 1/4 cups powdered sugar
1/2 cup heavy cream
Preheat oven to 350° and grease and line with parchment paper a 9-inch springform pan.
Pour the Guinness into a large saucepan and add the sliced butter. Heat until the butter is melted and remove from the heat. Whisk in the cocoa and sugar. In a separate bowl, beat the sour cream with the eggs and vanilla. Add the sour cream mixture to the Guinness mixture in the saucepan. Finally, beat in the flour and baking soda.
Pour the batter into the greased and lined springform pan and bake for 45 mins to an hour.(I baked mine for 53-55 minutes, checking with a toothpick for doneness and it came out well. Your oven may vary.) Cool completely in the pan on a wire rack.
For the frosting, beat the powdered sugar and cream cheese together until well combined and creamy. Add the cream and beat again until it's a spreadable consistency. I found slowly adding the cream and beating the icing very well gave excellent results. At first there seems like a lot of frosting for just the top of a 9-inch cake but don't skimp! The idea is to frost the top of the cake until it resembles the frothy head of a pint of Guinness. It's quite dramatic and lovely.