For the mousse, soak the gelatine in cold water for about 5 minutes. Mix crème fraîche, yoghurt, lemon juice, 50 g icing sugar and vanilla sugar. Squeeze the gelatine gently and dissolve at low heat.
Stir in 2 tablespoons of cream-fraîche mixture, then stir everything into the rest of the cream. Chill for 5-10 minutes until the cream begins to gel.
Beat the egg whites until stiff, adding 2 tbsp. icing sugar. Whip cream until stiff. As soon as the yoghurt mass begins to gel, fold in the cream first, then the beaten egg white. Cover and chill for 2-3 hours.
In the meantime thaw the raspberries. Puree with a hand blender and pass through a fine sieve. Sweeten with 2 tbsp. icing sugar. Divide the raspberry puree into four glasses.
Break the chocolate into pieces and melt in a hot water bath. Use two moistened tablespoons of the cream to cut off the cams and place them on the raspberry puree. Pour liquid chocolate into the freezer bag, cut off a small corner and draw it in strips over the cams.