Put all of the ingredients into a large bowl (200g self-raising flour, 40g cocoa powder, 230g caster sugar, 4 large eggs, 240g soft margarine, ¼ tsp vanilla extract, 2 tsp milk and the grated chocolate) mix on a low speed until fully combined.
Divide the mixture evenly between the two tins. Make sure you spread the mixture out so it is even.
Put the tins in the oven and cook for 50 minutes. After 50 minutes put a skewer in the middle and check if it comes out clean. If not, pop back in the oven for 10 more minutes and look again.
When cooked, remove the cakes from the oven and leave to cool in the tins for 20 minutes. After 20 minutes, remove the cakes from their tins and carefully peel off the greaseproof paper and pop them onto a wire rack to cool completely.
Once cooled, use a knife to carve off the top of the bottom cake (so it's flat and the top part of the cake will sit on it nicely).
Spread the lemon curd evenly on top of the bottom part of the cake.
Carefully place the top part of the cake on top.
To melt your chocolate coating, break the chocolate into squares and put into a glass bowl.
Place over a pan of barely simmering water.
You need to melt the chocolate very slowly, only stirring now and again or it will go hard. Be patient, it's worth it!