Giant Jaffa cake

Instructions

1. Mist a 22cm round springform cake tin with cooking spray, then line the base and sides with baking paper. Line an 18cm round sandwich tin with clingfilm.
2. In a large heatproof jug, dissolve the jelly in 285ml boiling water, then stir in 285ml cold water. Let cool slightly, then pour into the prepared sandwich tin, stopping ½cm below the rim. Chill in the fridge for 4 hours, or until set.
3. Preheat the oven to 180°C, fan 160°C, gas mark 4. To make the sponge, put the eggs and sugar in a large heatproof bowl set over a pan of simmering water, making sure the bowl doesn’t come into contact with the water. Whisk using a hand-held electric whisk for 6-8 minutes, or until thickened. Remove from the heat then fold in half the flour until combined. Repeat with the remaining flour. Pour into the prepared tin and bake for 20 minutes, or until a skewer inserted into the centre of the cake comes out clean. Leave in the tin to cool completely.
4. Meanwhile, make the mousse. Melt the chocolate in a heatproof bowl set over a pan of simmering water, making sure the bowl doesn’t come into contact with the water. Set aside to cool. Put the egg whites and sugar in a large bowl and whisk using a hand-held electric whisk until stiff peaks form. Stir the yogurt into the melted chocolate until combined, then fold the chocolate mixture into the meringue in 2 batches.
5. To assemble the cake, invert the jelly onto the cooled sponge in the springform tin, discarding the clingfilm. Spoon over the mousse, smoothing the top and sides using the back of a spoon. Chill in the fridge for 3 hours, or until set.
6. To serve, gently release the cake from the tin, then transfer to a cake stand. Top with the orange slices, and scatter over the zest.