Chocolate soured cream cake

Method

1. Heat the oven to 180°C/160°C fan/gas 4. Using an electric hand mixer, beat the 175g butter with the caster sugar in a mixing bowl until pale and fluffy. Beat in the eggs, 1 at a time, then beat in the vanilla, 100g melted chocolate, flour, cocoa powder and bicarb until combined. Finally, beat in the 150g soured cream. Divide between the 2 prepared tins, level the tops and bake for 30 minutes or until risen and springy to the touch. Cool in the tin for 5-10 minutes, then turn out onto a wire rack to cool completely.
2. For the filling, melt the dark/plain chocolate in the 100g soured cream in a bowl over a pan of simmering water (don’t let the bowl touch the water). Stir briefly, then leave to cool.
3. Make the buttercream by beating the butter with the icing sugar in a large mixing bowl until light and fluffy. Put a clean damp tea towel over the bowl when you start mixing to stop a cloud of icing sugar escaping. Once the mix is fluffy, beat in the soured cream and vanilla.
4. Put one of the sponges on a cake stand or plate and spread with the filling. Put the other sponge on top and cover with the buttercream, smoothing it all over. Use a palette knife to scrape the sides so you can see bits of the cake under the buttercream.
5. To finish the cake, melt 50g of the milk chocolate in a bowl set over a pan of simmering water (or in the microwave). Once melted, stir in the rest of the chopped chocolate, then spoon it over the cake, swirling it to marble the top and encourage it to run down the sides.