Battenberg cake

1. Preheat the oven to 200C/400F/Gas 6. 2. In a large bowl, beat the butter, sugar, eggs, vanilla, flour and milk together until smooth. Pour half of the cake mixture into another bowl. Add a drop of pink food colouring to one of the bowls and stir well. 3. Grease a 15cm/6in square cake tin. Place a thick layer of aluminium foil down the middle, covering the bottom, to divide the tin into two equal parts. Spoon the pink cake mixture into one side of the tin and the plain mixture into the other side. 4. Transfer to the oven and bake for 25-30 minutes, or until springy to the touch. Leave to cool on a wire rack. 5. Trim the cakes to the same size, then cut them both in half lengthways. 6. In a pan, heat the jam with a little water until it becomes liquid. 7. Place one of the pink pieces of cake onto a work surface and brush one side with jam. 8. Lay a yellow piece next to it on the jam side and push gently together. 9. Brush the tops of both pieces with more jam. Top the yellow piece of cake with a pink piece and vice versa. Brush the outside edges of the cake with more jam. 10. Cut the rolled marzipan so that it's just slightly longer than the cake. Wrap it around the cake, brushing the edges with a little jam to seal them together. 11. Trim off the excess marzipan at the ends and place the cake onto a plate, seal-side down. 12. Chill in the fridge for at least half an hour, then slice and serve.