Step 1

Make sure you read the tips and notes before you start.

Step 2

Step 1 - In a medium steel bowl, over a bain-marie, melt the dark chocolate, milk chocolate and butter together, until velvety smooth. Set aside.

Step 3

Step 2 - In a large mixing bowl, whisk together the sugar and the 3 egg yolks for about 5 minutes, until the mixture is pale and foamy, and a ribbon forms when you lift the whisk.

Step 4

Step 3 - In a separate large mixing bowl, beat the 6 egg whites and salt to a stiff peak.

Step 5

Step 4 - Pour the melted chocolate and butter in the egg yolk-sugar mixture and whisk to combine. Now with a spatula, fold about a ¼ or less of the egg whites into the chocolate mixture to lighten and loosen it. In three separate additions, fold in the rest of the egg whites very gently and stop mixing when just uniform.

Step 6

Step 5 - Immediately divide the mousse into individual serving cups (4 large or 6 small), cover with plastic film (make sure the film does not touch the mousse) and refrigerate for at least 3 hours (ideally 4-5 hours) before serving.

Step 7

Optional: for serving, top each chocolate mousse cup with a dollop of whipped cream and a dusting of cocoa powder.