Mix yoghurt, sugar and 1 packet of vanilla sugar. Line a large sieve with kitchen paper and hang in a bowl. Add the yoghurt and leave to drain in the fridge for at least 5 hours, preferably overnight
Clean, wash and thinly slice the rhubarb. Bring to the boil in a pot with about 1/4 cup of water, cover and stew for 3-5 minutes. Add 1 packet of vanilla sugar. Stir the jam sugar into the rhubarb and bring to the boil while stirring once. Let the compote cool down a little. Pour into a large bowl and allow to cool
Carefully turn out the yoghurt from the sieve onto a plate and remove the kitchen paper. Use two tablespoons of cold water to cut or shape cams and place them close together on the rhubarb. Decorate with lemon balm and dust with icing sugar