Step 1

For the cake:

Step 2

Preheat the oven to 350°F. Grease a 9-inch cake pan with a removable bottom and line with a disc of parchment paper.

Step 3

Melt the butter in a saucepan and then whisk in the cocoa powder and Guinness. Remove from the heat and set aside.

Step 4

In a large mixing bowl combine the flour, baking soda and sugar. Make a well with the back of a spoon and pour in the melted butter mixture along with the eggs, sour cream and vanilla extract.

Step 5

Pour batter into the prepared cake tin and place in the oven for 1 hour or until a skewer inserted comes out completely clean. When the cake is baking, make the cream cheese frosting.

Step 6

For the frosting:

Step 7

Melt the chocolate in a bowl placed on top of a saucepan filled with a little water boiling over a low heat. Remove from the heat to cool for about 10 minutes.

Step 8

Place the butter and cream cheese in a bowl and beat until fluffy and combined. Mix through the melted white chocolate and then gradually sift and beat in the icing sugar until you have a smooth, spreadable mixture.

Step 9

To assemble:

Step 10

Place the cake on a cake stand and spread with frosting.