Clean rhubarb, wash it. Cut into small pieces and weigh 600 g. Mix with jam sugar and 1 vanillin sugar in a large pot. Leave to stand for about 1 hour.
Bring to the boil while stirring continuously at high heat. Then simmer for a few minutes. Pour into preserving jars. Chill for about 1 hour.
Soak the gelatine in cold water. Mix yoghurt, sugar and 1 vanillin sugar. Squeeze the gelatine, dissolve over a mild heat, mix with 2-3 tbsp. yoghurt. Stir into the rest of the yoghurt. Keep cold until the cream starts to gel. Whip cream until stiff and fold in. Pour into the glasses. Cool for at least 4 hours. Decorate the yoghurt mousse with mint to taste