Mix 250g plain flour, 1.5 tsp baking soda, 1.5 tsp baking powder, pinch of salt, and 70g cocoa powder together
In another bowl, combine 100g white sugar and 200g soft dark brown sugar
Add 2 large eggs, 1.5 tsp vanilla extract, 100ml vegetable oil, and 200g creme fraiche or sour cream to the sugar mixture
Stir in 300ml Guinness and 100ml boiling water
Combine wet and dry ingredients
Pour into a 20cm x 30cm pan
Bake at 180°C in a conventional oven for 35 minutes
For frosting, cream together 100g butter and 300g cream cheese
Beat in 150g icing sugar and 1 tsp vanilla essence
Frost the cooled cake
