Butter gives this mousse a deliciously smooth texture, while whisking the egg yolks creates extra volume.
- Preparation time: 15 minutes, plus chilling
- Cooking time: 5 minutes
- Total time: 20 minutes, plus chilling
150g dark chocolate (70% cocoa), broken into small pieces
25g unsalted butter
5 eggs, separated
3 tbsp caster sugar
1. Melt the chocolate and butter in a bowl set over a pan of barely simmering water, stirring occasionally. Set aside to cool slightly.
2. Put the egg yolks and 1 tbsp sugar in a clean bowl; set over a pan of barely simmering water. Use electric beaters to whisk for 3-4 minutes, until pale. Take off the heat; stir in the chocolate mixture.
3. In a separate bowl, whisk the egg whites to stiff peaks with a pinch of salt. Beat in the remaining 2 tbsp sugar until stiff and glossy. Fold 1/3 of this into the chocolate mixture to loosen, then carefully fold in the remaining egg white, a third at a time, trying to retain in much air as possible. Tip into 4 glasses or ramekins (about 175ml capacity) and chill for at least 4 hours, until set, before serving.