In a large bowl over a medium heat, combine the Guinness and butter.

When the butter has melted, add the sugar and cocoa then blend together.

In another bowl, mix together the sour cream, vanilla extract and eggs.

Then add to the Guinness mix.

Add the baking soda and flour while mixing, then whisk well.

Pour into a large cake pan.

Place in an oven preheated to 350 F and bake for about 45 minutes.