for the frosting
125ml/4fl oz water - 30g/1oz dark muscovado sugar - 75g/6oz unsalted butter cubed - 300g/10oz best-quality dark chocolate finely chopped
1. Preheat the oven to 180C/350F/Gas 4. Line the bottoms of two 20cm/8in sandwich tins with baking parchment and butter the sides, then put the cocoa and the dark muscovado sugar into a large bowl and pour in the boiling water. Whisk to mix and set aside.
2. Cream the butter and caster sugar together in a separate bowl, beating well until pale and fluffy. Stir in the flour, baking powder and bicarb. of soda together and set aside.
3. Dribble the vanilla extract into the creamed butter and sugar mixing all the while then crack in 1 egg, followed by a scoop of the flour mixture, then the 2nd egg. Keep mixing after each addition while adding the rest of the flour mixture
little by little, finally mix and fold in the cocoa mixture, scraping the bowl well with a spatula.
4. Divide the chocolate & batter between the two prepared tins and put in the oven for about 30 minutes. Cool on rack for
5-10 minutes, then turn the cakes out and set aside to cool.
5. Melt the water, muscovado sugar and butter over a low heat, when it begins to bubble, take off the heat and add the chopped chocolate, swirling the pan and leave for a minute to melt. Once melted, whisk until smooth and glossy.
6. Set the frosting aside for about one hour, whisking now and again until the cakes will be cooled, and ready for the frosting.
7. Set one of the cooled cakes, with its top side facing downwards, onto a cake stand or plate, and spread with about one-third of the frosting. Top that with the second cake spread the remaining frosting over the top and sides.