Preheat fan forced oven to 160℃ and line 2 cake tins with baking paper.
Add Guiness and butter to mixer bowl. Cook for 4 min/90℃/speed 3/MC off.
Add cocoa and sugar. Mix for 10 sec/Speed 4/MC on.
Add sour cream, eggs and vanilla. Mix for 10 sec/Speed 4/MC on.
Add flour and b-carb. Mix for 10 sec/speed 4/MC on, scrape mixer bowl down.
Pour evenly into the 2 cake tins and bake in the oven for 35 -45 min, checking centre of cake is cooked through. Remove and cool completely in the cake tin before icing.
While the cake is baking make your icing, add icing sugar to mixer bowl and mix for 10 sec/speed 8/MC on to remove any lumps in the icing, scrape mixer bowl down.
Add cream and set machine to 2 min/speed 4/MC off and add cubes of cream cheese throughout the set time.
Once the cake is completely cooled, remove from the tin and trim the cake to be able to layer evenly. Place one cake layer on your plate and add about one third of the icing and spready evenly over the top of the cake. Add the second cake layer and add the remainder of the icing only to the top off the cake spreading evenly leaving little peaks.