Chocolate Orange Battenberg Cake

1. Preheat the oven to 200°C/gas mark 6 or 180°C if using a fan oven. Use a little butter to grease a deep-sided 20cm square cake tin, then line with baking parchment.
2. Tear a sheet of tin foil, around 12cm width, then fold into three to make a strip around 4cm width. Wrap in baking parchment and fold in the ends to secure. Sit it upright in the baking tin, half-way, as this will separate the two different cake batters for baking.
3. Pour the sugar into a large bowl, then add the butter. Beat for a few minutes until the mixture is pale, fluffy and light. Beat in the orange zest.
4. Carefully fold in the 250g flour in three stages, then fold in the orange juice.
5. Shake the carton of OGGS® Aquafaba then whisk in a bowl until thick and moussey. Fold a large spoonful into the flour mixture, then fold in the rest and mix until smooth.
6. Spoon just under half your mixture into a separate bowl and beat in the cocoa and dark chocolate until thoroughly combined. Give it a good beat if there are still a few floury patches. Then into the other bowl, fold in the 1tbsp flour.
7. Spoon the plain cake batter into one side of the tin and the chocolate batter into the other side of the tin, so the two are separated by the foil-covered strip. Level each one.
8. Bake in the oven for 40-45 minutes. The cakes are ready when you push a cocktail stick into the middle and it comes out clean. Cool in the tin for around 1 hour.
9. Cover the tin with a board then, holding both of them together, turn the tin upside down and let the sponge gently slide onto the board. Take off the parchment and carefully cut down the middle to separate the two sponges, removing the strip in the middle as you do so. Trim any crumbly bits until you have two rectangles, each around 8cm width. Chill in the fridge, still on the board, for 30 minutes.
10. Take the board out of the fridge and cut each rectangle lengthways into four long rectangles, each 4cm width. Return the cake, still on the board, to the fridge and chill for another 30 minutes.
11. Put the marmalade into a bowl and stir in 1 tsp boiling water. Mix well until smooth. Separate the lengths of sponge – be careful with them as they might be crumbly! – and put one plain length and one chocolate length next to each other. Brush the marmalade in between and push together. Brush the marmalade over the top of each one, then sit the other length of plain sponge on top of the chocolate one so it’s diagonally opposite the other plain one. Brush the middle side, then put the chocolate on top the other side and gently press together. It’ll look like a chequerboard. Return to the fridge while you roll out the marzipan.
12. Line a board with a large piece of parchment and roll out the marzipan until it measures a rough rectangle, around 32 x 20cm. Use a little icing sugar, if the marzipan is sticky.
13. Brush the remaining marmalade all over the marzipan. With the shortest side of the marzipan horizontal to you, carefully transfer the cake so it sits with the longest edge horizontal and lift the marzipan up and around the cake, using the parchment to help. Seal the edges together then press the marzipan into the cake to secure, keeping it wrapped in the parchment. Chill again for 20 minutes.
14. Unwrap the parchment and trim the ends, then slice and serve.

Top tip: For the finishing touch, scatter fine strands of orange zest all over the cake before serving.