My wonderful husband found this recipe from one of my favorite chef's Nigella Lawson. I made it a couple weeks ago and it was beyond amazing.
Preheat oven to 350 F, and butter and line a 9 inch springform pan.
Pour the 1 cup Guinness into a large wide saucepan, add 1 stick plus 2 Tbsp. unsalted butter in spoons or slices and heat until the butter's melted, at which time you should...
...whisk in 3/4 cup unsweetened cocoa and 2 cups sugar. Beat in 3/4 cup sour cream, 2eggs and 1 tsp. vanilla.
Finally whisk in 2 cups all-purpose flour and 2 1/2 tsp. baking soda.
Pour cake batter into the greased and lined pan and bake for 45 minutes to an hour. Leave to cool completely in the pan on a cooling rack, as it is quite a damp cake.
When cake is cold, sit it on a flat platter or cake stand and get on with the frosting.
Lightly whip 8 oz. cream cheese until smooth, sift over 1 1/4 cups confectioner's sugar and then beat them both together.
Add 1/2 cup heavy cream and beat again until it makes a spreadable consistency.
Ice the top of the black cake so that it resembles the frothy top of a Guinness.
It's a very rich cake...went well with coffee.