Soak gelatine in cold water. Wash the strawberries and put 4 pieces aside. Clean and puree the remaining strawberries. Mix quark, 1 tablespoon sugar, vanillin sugar and strawberry puree. Squeeze the gelatine and melt in a small pot.
Stir in 3 tablespoons of quark cream, then stir into the rest of the cream.
Beat the egg whites until stiff, adding 2 tablespoons of sugar. Whip the cream until stiff as well. Carefully fold both into the quark. Spread the mousse over 4 glasses. Cover and chill for at least 2 hours.
Decorate the mousse with strawberries before serving.