This is a River Café Cookbook recipe. Over the years, I have tried varying it by adding chopped crystallised and stem ginger, rum-soaked raisins, lime zest, vanilla extract, cardamom, and coffee instead of some of the cocoa, but I always come back to the original, which I’ve now decided I can’t improve on. Pressing it makes it particularly rich and dense, but I once forgot and it was still delicious. Serve it warm or cold with crème fraiche.
200g dark chocolate, 70% cocoa solids
150g unsalted butter
5 large eggs, separated
2 tbsp cocoa powder
115g caster sugar
Icing sugar to decorate.
Preheat the oven to 180C/fan oven 160/Gas Mark 4.
Butter and flour a shallow 20cm loose-bottomed cake tin. Melt the chocolate with the butter in a bowl over a saucepan of water that's just below simmering point (make sure the water doesn't touch the bowl). Remove from the heat just before the chocolate has completely melted. Allow to cool for a few minutes, then whisk in the egg yolks. Stir in the cocoa and sugar.
Beat the egg whites until they form soft peaks. Using a metal spoon carefully fold them into the chocolate mix, a third at a time, until no white remains. Pour the mixture into the tin and bake for about 30 minutes untiil it has risen like a soufflé.
Put a plate that fits neatly into the tin on top of the cake and weight it (e.g. with a small can). Leave it for 30 minutes, then turn the cake out and dust lightly with icing sugar when cool.