250g dark chocolate, broken into chunks - standard supermarket chocolate is fine
300g self-raising flour
300g light, soft brown sugar, plus 2 tbsp
200ml sunflower oil, plus a little extra for greasing
284ml soured cream
1 tsp vanilla essence
500g white caster sugar
1 tsp vanilla extract
1 tbsp liquid glucose
2 egg whites
25g icing sugar, sifted
Heat oven to 160C/fan 140C/gas 4 and grease and line a deep, 20cm round cake tin. Whizz the chocolate in a food processor until crumbs. Tip the flour, sugar, cocoa, oil, 150ml soured cream, eggs, vanilla and 150ml water into the largest mixing bowl you have. Whisk with an electric whisk until smooth, then quickly stir in 150g of your whizzed-up chocolate bits. Scrape into a tin, and bake on the middle shelf for 1 hr 20-1 hr 30 mins, or until a skewer inserted in the centre comes out clean. Cool in the tin.
While the cake is baking, make the icing. Combine remaining chocolate bits and soured cream with 2 tbsp soft brown sugar in a small saucepan and heat, stirring, until the chocolate is melted and you have a smooth icing. Leave to cool.
When the cake is cool, slice it into 3 even layers. Spread 2 layers with chocolate icing.
To make the angel frosting, put the sugar, vanilla and liquid glucose in a pan with 125ml water. Bring to the boil and cook just until the sugar has melted and the syrup turns clear. Take off the heat. Meanwhile, beat the egg whites until stiff, then continue beating, gradually pouring in the hot sugar syrup in a steady stream, until the mixture is fluffy and thick enough to spread - this might take a few mins as the mixture cools. Beat in the icing sugar. Work quickly and spread a tiny bit over each chocolate-covered layer. Assemble cake and swirl remaining frosting over entire cake.