Based on a Nadiya Hussain recipe. Melt 50g dark chocolate. Cream together 200g unsalted butter and 200g caster sugar with an electric beater until light
and creamy, add the zest of an orange and 5 beaten eggs, one by one, then pour in the melted chocolate, mixing well, followed by 200g self-raising flour, sifted,
120g cocoa powder, sifted, and 1 tsp baking powder. Mix well, until you have a smooth thick mixture, then divide equally between two greased 20cm cake tins,
lined with a disk of baking parchment. Bake in a 180°C oven for 25 minutes, until a skewer comes out clean. Take out of the oven and pour over the squeezed
juice from two oranges (zest the other orange before squeezing, as you will need this for the ganache!). Lert the cakes cool for 15 minutes, then turn out
onto a rack. Make a ganache by heating 200ml double cream almost to boiling, then pour this over 200g dark chocolate, broken into small pieces. Stir until
the chocolate has melted and it is thick and glossy. Stir in the grated orange zest. Place one of the cakes onto a serving plate and spread on a thin layer
of marmalade, then cover this with a third of the ganache. Place the other cake on top and spread the rest of the ganache on the top and sides.