I have made a lot of chocolate cakes. Some were too dry. Some were too sweet. Some had that strange artificial taste of cocoa powder you have not bought recently. This one is none of those things. It is deeply, intensely chocolatey — the kind of cake where the first bite makes conversation stop. I make it for every birthday, and I have never had leftovers.
The Secret: Hot Coffee
The single most important thing in this recipe is hot, strong coffee added to the batter. It does not make the cake taste of coffee — it amplifies and deepens the chocolate flavour in a way that nothing else does. Use good instant coffee dissolved in boiling water if you do not have a machine. 240ml of it goes straight into the batter.
The Cake
Combine 200g plain flour, 400g caster sugar, 85g Dutch-process cocoa powder, 2 tsp baking soda, 1 tsp baking powder, and 1 tsp salt in a bowl. In a separate bowl, whisk 2 eggs, 240ml buttermilk, 120ml vegetable oil, 1 tsp vanilla extract, and the hot coffee. Combine wet and dry ingredients and mix until smooth — the batter will be thin and pourable. Divide between two greased 23cm tins and bake at 180°C for 35 minutes.
The Frosting
Melt 280g of 70% dark chocolate and let it cool slightly. Beat 225g of softened butter until pale, add 350g of icing sugar gradually, then beat in the melted chocolate and 120ml of double cream. The frosting should be glossy and spreadable. Fill between the layers generously, crumb-coat, refrigerate briefly, then apply the final coat. Finish with chocolate curls or flaked sea salt.