Mousse au chocolat

Method

1. 1 Melt the dark chocolate and unsalted butter in a double boiler until smooth, then let cool for 5 minutes.
2. 2 Separate the eggs and stir the yolks into the chocolate mixture until well combined.
3. 3 Beat the egg whites with a pinch of salt until fluffy, then add the sugar and continue beating until stiff and glossy.
4. 4 Fold the egg whites into the chocolate in three stages, gently mixing from the bottom up to retain the air bubbles.
5. 5 Pour into glasses, refrigerate for at least 2 hours until the mousse sets smoothly, then serve.