From Feast by Nigella Lawson (reprinted in the New York Times on 12/8/04)

Yield: One 9-inch cake (12 servings)

For the cake:

Butter for pan
1 cup Guinness stout
10 tablespoons (1 stick plus 2 tablespoons) unsalted butter
3/8 cup unsweetened cocoa
2 cups sugar
3/8 cup sour cream
2 large eggs
1 tablespoon vanilla extract
2 cups all-purpose flour
2 1/2 teaspoons baking soda

For the topping:

1-1/4 cups confectioners’ sugar
8 ounces cream cheese, at room temperature
1/2 cup heavy cream

For the cake: Heat oven to 350 degrees. Butter a 9-inch springform pan and line with parchment paper. In a large saucepan, combine Guinness and butter. Place over medium-low heat until butter melts, then remove from heat. Add cocoa and superfine sugar, and whisk to blend.

In a small bowl, combine sour cream, eggs and vanilla; mix well. Add to Guinness mixture. Add flour and baking soda, and whisk again until smooth. Pour into buttered pan, and bake until risen and firm, 45 minutes to one hour. Place pan on a wire rack and cool completely in pan.

For the topping: Using a food processor or by hand, mix confectioners’ sugar to break up lumps. Add cream cheese and blend until smooth. Add heavy cream, and mix until smooth and spreadable.

Remove cake from pan and place on a platter or cake stand. Ice top of cake only, so that it resembles a frothy pint of Guinness.