Preheat the oven to 180°C, 160°C fan oven, Gas mark 4.
Place all ingredients except for chocolate in a mixing bowl and beat for 2-3 minutes until smooth. Spoon half of the batter into a separate bowl.
Mix the chocolate into the batter in one of the two bowls.
Place alternate spoonfuls of each colour batter into the cake tin.
Briefly swirl the two colours of batter together so the two colours are still distinctly visible.
Bake in the preheated oven for 40-50 minutes until cooked and golden brown. Leave the cake in the tin for 2 minutes before tipping it out on a wire rack. Cut the cake into slices.
- Temperature: 180 oC
- Baking time:
- Serves: 16