Mix the egg yolks with the REGILAIT powdered semi-skimmed milk, 20g powdered sugar, orange juice and bitter cocoa powder.
Whip the egg whites into peaks, then add the rest of the powdered sugar and beat for a further 30 seconds.
Add _ of the egg whites to the cocoa mixture to soften up the mixture, then gently fold in the remaining egg whites with a spatula, taking care not to let the peaks collapse.
Leave the mousse in the fridge for at least 3 hours before serving.

Chef’s tip:
You can use a 200g bar of plain chocolate melted in a bain-marie instead of the bitter cocoa powder.
To decorate your mousse with chocolate flakes simply scratch the surface of a chocolate bar with a knife.