1. In a thick-bottomed saucepan, melt the sugar in 1 tablespoon of water. Pour onto a pastry plate covered with a silicone mat (silpat) or wax paper.
2. Let cool. Crush the crunch in a robot and set aside.
3. Break the chocolate into small pieces in a bowl, then melt in a double boiler. Set aside off the heat. Add the butter in small cubes.
4. Separate the egg whites from the yolks. Beat the whites until stiff. Whip the cream.
5. Add the egg yolks to the melted chocolate, mix to obtain a creamy mixture.
6. Incorporate the stiffened egg whites gently with a spatula, little by little, to avoid losing the mousse texture.
7. Add the whipped cream and caramel crunch, mixing gently.
8. Refrigerate for 2 hours before serving.