Step 1

Heat oven to 180C/160C fan/gas Grease two 900g loaf tins (8.5cm deep) and line with baking parchment.

Step 2

First, make the chocolate cake mixture. Put the butter and chocolate in a large heatproof bowl set over a pan of simmering water, stirring occasionally. Put all the other ingredients in a large mixing bowl and, when the chocolate and butter have melted, pour over and mix with an electric whisk until smooth and well combined. Set aside and rinse the beaters.

Step 3

In another large bowl, add all the sesame cake ingredients, then combine with an electric whisk until smooth.

Step 4

Alternating with dollops of each mixture, divide between the two tins. Level the top, then swirl a skewer through the mixture to create a marbled effect. Bake in the middle of the oven for 45-50 mins or until a skewer inserted into the centre comes out clean. Leave the cakes to cool completely on a wire rack while you make the topping (there’s enough for both cakes but the topping recipe is easily halved if you want to freeze one and ice it later)

Step 5

Heat the double cream and butter together gently in a small pan until just simmering, then remove from the heat and add the chocolate. Stir until the mixture is smooth, then place in the fridge for 20 mins to firm up.

Step 6

Beat well with a wooden spoon, then transfer to a disposable piping bag. Snip the end off to make a wide opening, then pipe thick, overlapping zigzags across the cakes. Cut the sesame snaps into shards and arrange on top, scattering over any crumbs, then serve.