For the cake:
- 200g (8 oz) plain flour
- 200g (8 tbsp) caster sugar
- 5ml (1 tsp) baking powder
- 2.5ml (½ tsp) bicarbonate of soda
- 40g (1½ oz) best-quality cocoa
- 175g (6 oz) soft unsalted butter
- 2 large eggs
- 10ml (2 tsp) real vanilla extract
- 150ml (¼ pint) sour cream
For the Icing:
- 85ml (3 oz) unsalted butter
- 175g (6 oz) best-quality dark chocolate, broken into pieces
- 300g (10 oz) icing sugar
- 15ml (1 tbsp) golden syrup
- 125ml (4fl oz) sour cream
- 5ml (1 tsp) vanilla extract
- sugar flowers (optional)
- Take everything out of the fridge so all the ingredients can come to room temperature. Heat oven to 180°C/fan 160°C/gas 4 and line and butter two 20cm sandwich tins with removable bases. Now all you have to do is put all the cake ingredients (flour, sugar, baking powder and bicarb, cocoa, butter, eggs, vanilla and sour cream) into a food processor and process until you have a smooth thick batter. If you want to go the long way round, just mix the flour, sugar and leavening agents in a large bowl and beat in the soft butter until you have a combined and creamy mixture. Now whisk together the cocoa, sour cream, vanilla and eggs and beat this into your bowl of mixture.
- Divide this batter, using a rubber spatula to help you scrape and spread, into the prepared tins and bake until a cake tester, or a thin skewer, comes out clean, which should be about 35 minutes, but it is wise to start checking at 25. Also it might make sense to switch the two cakes around in the oven halfway through cooking time. Remove the cakes, in their tins, to a wire rack and let cool for 10 minutes before turning out of their tins. Don’t worry about any cracks as they will easily be covered by the icing later.
- To make this icing, melt the butter and chocolate in a good-sized bowl suspended over a pan of simmering water. Go slowly you don’t want any burning or seizing. While the chocolate and butter are cooling a little, sieve the icing sugar into another bowl. Or, easier still, put the icing sugar into the food processor and blitz. This is by far and away the least tedious way of removing lumps. Add the golden syrup to the cooled chocolate mixture, followed by the sour cream and vanilla, and then, when all this is combined, whisk in the sieved icing sugar, with the motor running.
- When you’ve done, you may need to add a little boiling water, say a teaspoon or so, or indeed some more icing sugar. It depends on whether you need the icing to be runnier or thicker; or indeed it may be right as it is. It should be liquid enough to coat easily, but thick enough not to drip off.
- Choose your cake stand or plate and cut out four strips of baking parchment to form a square outline on it (this stops the icing running onto the plate). Then sit one of the cakes, uppermost (i.e. slightly domed) side down. Spoon about a third of the icing onto the centre of the cake half and spread with a knife or spatula until you cover the top of it evenly. Sit the other cake on top, normal way up, pressing gently to sandwich the two together. Spoon another third of the icing onto the top of the cake and spread it in a swirly, textured way (though you can go for a smooth finish if you prefer, and have the patience). Spread the sides of the cake with the remaining icing and leave a few minutes till set, then carefully pull away the paper strips.