Defrost the berries. Separately soak 2 gelatine leaves in cold water
Mix yoghurt, 2 tablespoons sugar and vanilla sugar. Squeeze out 2 sheets of gelatine and dissolve over a mild heat. First mix with 2-3 tbsp. yoghurt, then stir into the remaining yoghurt
Puree the raspberries, except for a few for decoration. Season to taste with 2-3 tablespoons of sugar. Heat 3 tablespoons of puree. Squeeze 2 sheets of gelatine and dissolve in it. Stir into the rest of the puree. Chill for about 15 minutes.
Whip the cream until stiff, fold into the yoghurt. Layer mousse and puree alternately in glasses. Chill for at least 4 hours. Decorate with pistachios, rest of berries and lemon balm