Mocha coffee marble cake

1. Preheat the oven to 180ºC, gas mark 4, and line a large 1kg loaf tin with baking parchment. Melt the chocolate in a medium-sized heatproof bowl. When melted, set aside to cool slightly.

2. Cream the butter and sugar together in a large bowl until really light and fluffy. Add the eggs one at a time and beat well between each addition. Add the flour and baking powder, then beat until the batter is smooth and silky.

3. Add 1/3 of the cake mixture (approximately 225g) and 1 tbsp milk to the chocolate. Stir until combined, then set aside. Transfer half the remaining plain mixture into another bowl and add the cooled coffee. Stir until combined, then set aside. Stir the remaining milk into the rest of the plain batter. You should have 3 bowls of batter of a similar consistency.

4. Spoon the mixture into the loaf tin, alternating the different batters, ideally in concentric circles in places, by positioning each spoonful on top of each other to get a lovely rippled effect. 

5. Swirl the mixture gently with a skewer, then bake for 50-60 minutes until the sponge is golden and a skewer inserted comes out clean. Allow to cool completely in the tin, then slice to serve. This will keep well for up to 3 days in a cake tin.