In a large mixing bowl, combine the flour and baking soda and then set off to the side as well.

In a wide sauce pan, add the remaining 10 tablespoons of butter with the beer. Heat on medium-low until melted. Once melted, stir in the sugar and cocoa powder.

Meanwhile in a separate bowl, whisk together the sour cream, eggs and vanilla extract. Then add this mixture into the cocoa/beer mixture and whisk to combine.

Pour the chocolate mixture into the bowl with the flour and stir until incorporated, then pour the chocolate Guinness cake batter into the prepared pan.

Bake on the middle rack of your preheated oven for 40 to 45 minutes or until a cake tester comes out with only a trace of batter attached.

Allow the cake to cool before frosting.

In a medium bowl, beat the cream cheese until smooth. Gradually add in the powdered sugar and the milk. If frosting is too thick, add more sifted powdered sugar. If too thick, thin out with a little more milk.

Once the frosting is smooth, frost only the top of the cake, leaving the sides of the dark brown cake exposed. The cake should resemble a pint of Guinness.