Flavour this rich, dark marble cake with Guinness and prosecco – the luxurious soft cheese icing represents the settling bubbles of stout when it’s poured.
1. Heat the oven to 180C/fan 160C/gas 4. Butter a 900g loaf tin and line with a strip of baking paper overhanging either end.
2. Warm the butter, Guinness and chocolate in a small pan over a low heat until melted and smooth, then cool for 5 minutes.
3. Meanwhile, make the marble layer. Beat together the butter and sugar until pale. Beat in the egg, then the flour, followed by the wine.
4. Whisk the eggs into the cooled chocolate mixture, followed by the sugar and soured cream. Sift over the flour and cocoa and mix until just combined. Pour the Guinness batter into the tin and smooth over the top. Add the marble batter to the tin in dollops over the top (it will sink into the darker batter). Use a chopstick to slightly swirl the batters together, making swirls like a settling pint of stout.
5. Bake for 1 hour-1 hour 10 minutes or until a skewer poked into the middle comes out clean. Cool for 10 minutes in the tin, then use the overhanging paper to lift the cake from the tin onto a cooling rack. Cool completely.
6. For the frosting, beat together the butter and sugar in a bowl until pale and fluffy. Beat in the wine until incorporated, then add the soft cheese and mix until just combined – don’t over-mix, or the frosting will become runny.
7. Spoon the frosting over the cake, smoothing over the sides of the cake with a palette knife so you get defined, straight lines like the head of a black velvet cocktail. Dust with a little cocoa and chill until ready to serve.