Preheat the oven to 350 degrees. Grease and line a 9" spring form pan with parchment paper.

In a large saucepan, combine Guinness and butter. Heat over medium-high heat until the butter melts. Whisk in cocoa powder and sugar.

In a medium bowl, beat together the sour cream, eggs and vanilla, Pour into the beer and butter mixture, whisking to combine. Whisk in flour and baking soda.

Pour batter into the spring form pan. Bake for 45 minutes to 1 hour. Cool completely.

Lightly whip the cream cheese until smooth. Beat in confectioners' sugar and then the cream until it's spreadable.

Ice the top of the cooled cake.