melt the chocolate
Place chocolate in a large bowl and set over a bain marie (saucepan filled with water - but make sure the bowl isn't touching the water) at a low simmer. Stir chocolate until melted. Turn off the heat and let stand. In a separate saucepan bring 50g of whipping cream to a boil, then immediately remove from the heat and pour over the melted chocolate. Stir to combine to get a nice, glossy texture. Leave to cool to room temperature.
whip the egg whites and whipping cream
In a bowl whip the egg whites using a mixer. Gradually add the sugar and pinch of salt. Beat until firm peaks form. In a separate bowl whip 100g whipping cream until soft peaks form (make sure to use clean beaters).
Stir 1/3 of whipped cream and egg whites into cooled chocolate mixture, then gently fold in the rest with a rubber spatula. Spoon your chocolate mousse into serving dishes and put in a fridge for at least 3 hours or even better overnight.
Bring chocolate mousse to room temperature before serving (30 minutes). Top with whipped cream, shaves chocolate, cocoa nibs or chopped hazelnuts, if desired. Store in a fridge for up to 3 days. Enjoy.