1. pre-heat the oven to 140 fan. grease and line a 23cm spring form cake tin. 2. Melt the butter together with the dark chocolate in a bowl over a pan of simmering water. 3. Whisk the egg yolks and sugar until pale and smooth. add the chocolate and stir together. 4. Whisk the egg whites into firm peaks and fold into the chocolate mixture. pour into the cake tin and bake for 35-40 minutes or until a skewer comes out just clean from the side and still gooey in the middle. leave to cool. 5. Whisk the cream into soft peaks and spread over the top of the cake. grate over the plenty of chocolate and serve immediately