In a medium, pot, add the fruit, stout, butter, sugar, and baking soda and bring to a boil. Simmer over low heat for 15 minutes. Stir regularly, keeping a watchful eye to prevent the liquid from bubbling over. Set aside to cool *this can be made the day before and left overnight.
Preheat the oven to 150C and line a 23cm cake tin with baking paper on all sides.
Sift the flour and baking powder into a bowl.
Add the egg and the cooled fruit mix and stir by hand until well incorporated.
Tip the batter into the prepared tin and bake for 1 ½ hours (90 minutes).
I love to serve this cake 'naked' with fresh fruit as a garnish. It really doesn't need anything else.