Soak the gelatine in cold water. Mix yoghurt, 3 tablespoons sugar and vanilla sugar. Squeeze the gelatine and dissolve over a mild heat. First stir in 3 tbsp. yoghurt, then stir into the remaining yoghurt. Chill the cream for 10-15 minutes.
Whip the cream until stiff. As soon as the cream starts to gel, fold in the cream. Pour the cream into four cold rinsed moulds (approx. 175 ml each), refrigerate for at least 3 hours.
Clean, wash and cut the rhubarb into pieces. Boil up the cherry juice. Stir half the sauce powder, 1 tbsp. sugar and 2 tbsp. water until smooth. Stir into the boiling juice, bring to the boil and simmer for about 1 minute.
Add rhubarb and simmer for 2-3 minutes. Let the compote cool down.
Stir the rest of the sauce powder, 1 tbsp. sugar and 2 tbsp. milk until smooth. Boil up the rest of the milk. Stir in sauce powder, bring to the boil and simmer for about 1 minute. Dip the moulds briefly in hot water up to the rim. Turn out the tartlets.
Dress everything.