Ultimate chocolate cake

1.  Heat the oven to 160C/fan140C/gas 3. Butter and line a 20cm round cake tin (7.5cm deep).
2. Put the dark chocolate in a medium pan with the butter. Mix 1 tbsp instant coffee granules into 125ml cold water and pour into the pan. Warm through over a low heat just until everything is melted – don’t overheat. Or melt in the microwave for about 5 minutes, stirring halfway through.
3. Mix the self-raising flour, plain flour, bicarbonate of soda, light muscovado sugar and golden caster sugar with the cocoa powder and squash out any lumps. Beat the eggs with the buttermilk.
4. Pour the melted chocolate mixture and the egg mixture into the flour mixture and stir everything to a smooth, quite runny consistency.
5. Pour this into the tin and bake for 1hr 25 – 1hr 30 mins. If you push a skewer into the centre it should come out clean and the top should feel firm (don’t worry if it cracks a bit). Leave to cool in the tin (don’t worry if it dips slightly), then turn out onto a wire rack to cool completely. Cut the cold cake horizontally into three.
6. To make the ganache, put the dark chocolate in a bowl.  Pour the cream into a pan, add the golden caster sugar and heat until it is about to boil. Take off the heat and pour it over the chocolate. Stir until the chocolate has melted and the mixture is smooth. Cool until it is a little thicker but still pourable.
7. Sandwich the layers together with just a little of the ganache. Pour the rest over the cake letting it fall down the sides and smooth over any gaps with a palette knife. Decorate with grated chocolate or a pile of chocolate curls. The cake keeps moist and gooey for 3-4 days