Rich chocolate cake

Preheat the oven to 180°C/gas mark 4

Grease the inside of the cake tin with a little butter and line the base with a cut out circle of greaseproof paper

Break the chocolate into pieces and place into a heatproof bowl with the butter. Fill a small saucepan with a small amount of water, so the water is 3cm high in the pan, and bring to a simmer. Set the bowl over the saucepan, the base of the bowl should not touch the water and the water should not spill into the bowl

Stir the chocolate and butter gently so that it evenly melts. Once almost melted, remove from the heat and stir gently to finish the melting process. Set aside

Break the eggs into a large mixing bowl. Add the vanilla extract and whisk until just combined

Add the sugar and whisk on full power until the mixture reaches a pale, thick, mousse-like consistency with plenty of air - about 5 times the volume of the original mixture

Pour the melted chocolate mix onto the mousse and gently fold together using a metal spoon or spatula, do not beat. The two should combine fully and there should not be any chocolate left at the bottom

Pour the mixture into the prepared tin and bake for at least 35 minutes, or until firm to the touch and the centre is slightly moist under the crust

Remove from the oven and stand the tin on a wire rack. Run a knife around the edge of the tin and allow to cool. When cold remove from the tin by undoing the spring tin and turning the cake upside down onto a flat plate or cake stand and gently pull off the greaseproof paper

To make the topping, break up the chocolate into a large heatproof bowl with the cream

Using the same method as in step 3, begin to melt the chocolate and cream over simmering hot water in a saucepan. When the mixture is half-melted, remove from the heat and beat together until smooth

Pour the chocolate sauce evenly over the cake. Leave the sauce to firm until set, then serve