115g best-quality dark chocolate (90 per cent) 225g best-quality dark chocolate (70 per cent) 225g unsalted butter 460g caster sugar 4 eggs
1tsp vanilla essence 75g plain flour
33cm x 23cm baking tin
Preheat the oven to 160C/325F/ Gas 3. Generously grease the baking tin and line the base, greasing the paper too.
Break the chocolate into pieces. Melt the chocolate and butter over a double boiler or bain-marie. Pour the mixture into a mixing bowl or the bowl of electric mixer. Add the sugar and beat until smooth. Add the eggs, vanilla essence and ½tsp sea salt and beat well. Gently fold in the flour until no lumps remain.
Pour the batter into the tin and smooth the top. Bake for 40 minutes until the sides begin to pull away from the tin. Cool in the tin before cutting.