Heat the oven to 180C/375F/gas mark 4. Butter and line two 400g loaf tins (I used two 8x4in loaf tins to make a four section cake).

Cream together the butter and sugar then whisk in the flour and eggs, divide the mixture in half and mix the Chambord and red food colouring into one half, and 35g (4tbsp) of the cocoa and the milk into the other. Spoon the chocolate mix into one tin and the raspberry into the other, level the surface and bake for 25-35 minutes until a skewer inserted into the centre comes out clean.

Leave the cakes to cool in the tins for about 10 minutes then turn out onto a wire rack to cool completely.

Knead the remaining cocoa powder into the marzipan until it is well combined then roll it out into a rough rectangle, wide enough to wrap around the cakes when stacked.

Trim the tops of the cakes if necessary so that they are flat and the same height (I had to trim the chocolate one but not the raspberry). Lay one loaf on top of the other and trim all of the edges so that they are straight and the cakes are the same size.

If you used the 400g tins, cut each cake into quarters lengthways, turn each on its side and cut in half lengthways again, so you end up with 8 long strips of each cake. Lay a chocolate cake strip in the centre of the marzipan and trim the marzipan in a straight line at each end so it matches the length of the cake. Brush the cake all over with jam, lay a raspberry strip next to it and brush with jam, then another chocolate strip, then another raspberry. Push together tightly, brushing with more jam if needed; repeat until the cake is 3 squares high by 3 squares wide, then fold the marzipan over the cake, brushing the overlap with jam to seal. Turn the cake over so that the seam is on the bottom then serve (there will be leftover cake strips).

If you used the larger tins as I did, measure the height of the cakes, then cut two strips lengthways from each cake the same width as the height, lay one chocolate strip on the marzipan, trim the marzipan to the same length as the cake, brush the strip of cake all over with jam and lay a raspberry strip next to it, brush with jam then lay the other chocolate strip on top of the raspberry one, brush with jam, lay the other raspberry strip on top of the chocolate one, brush with jam then fold the marzipan over the cake, brush the overlap with jam and turn the cake over so that the seam is underneath then serve.