250g dark chocolate
Grate a small amount of chocolate and set aside.
Separate the egg whites from the yolks.
Beat the egg whites.
(Don't whip the cream.)
Melt the block of chocolate and mix with the cream and egg yolks.
Fold in the egg whites.
Cover the bowl and leave the mousse to sit overnight in the fridge.
Sprinkle the grated chocolate on top.