Chocolate Guinness Cake

Butter, for the pan

• 1 cup Guinness stout
• 10 tablespoons (1 stick plus 2 tablespoons) unsalted butter (see Tip)
• 3/4 cup unsweetened cocoa
• 2 cups superfine sugar
• 3/4 cup sour cream
• 2 large eggs
• 1 tablespoon vanilla extract
• 2 cups all-purpose flour
• 2 1/2 teaspoons baking soda
• 1 1/4 cups confectioners' sugar
• 8 ounces cream cheese at room temperature
• 1/2 cup heavy cream

1. 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.
2. 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 1 hour. Place pan on a wire rack and cool completely in pan.
3. 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.
4. 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.