Chocolate cloud cake

Method

1. Preheat the oven to 180°C/fan160°C/gas 4. Grease and line a 23cm round springform cake tin with baking paper. Melt the chocolate in a bowl set over a pan of simmering water or in the microwave (see How To… in the Know How section of the website). Stir the butter into the chocolate.
2. Beat the 2 whole eggs and 4 egg yolks with 75g caster sugar until smooth, then gently stir in the chocolate mixture, 2 tablespoons of the Cointreau and zest, if using.
3. In another bowl, whisk the 4 egg whites until foamy, then gradually add the remaining 100g of sugar and whisk until the whites hold their shape, but aren’t too stiff. Lighten the chocolate mixture by beating in a dollop of egg white, then fold in the rest of the whites. Pour into the tin and bake for about 35-40 minutes or until the cake is risen and cracked and the centre is no longer wobbly. Cool the cake in the tin on a wire rack; the middle will sink as it cools.
4. Place the base on a cake stand or plate before carefully removing from the tin. Whip the double cream until soft, then add the vanilla extract and remaining Cointreau, if using, and whisk until the cream is firm but not stiff. Fill the crater with the whipped cream, easing it out gently towards the edges, and dust the top lightly with cocoa powder sieved through a tea strainer.