Clean, wash and cut the rhubarb into pieces. Bring rhubarb, 125 g sugar, vanillin sugar and 3/8 litres of water to the boil. Cook over medium heat for about 5 minutes. Mix 50 g starch with a little cold water and thicken the rhubarb with it. Fill the rhubarb groats into 4 bowls and chill. For the sauce, put milk, except 4 tablespoons, in a pot. Cut the vanilla pod lengthwise.
Scrape out the pulp and add to the milk with the pod. Add 30 g sugar and salt and bring to the boil. Mix 30 g starch and 4 tablespoons of milk, stir into the milk, bring to the boil and simmer for 1-2 minutes. Mix egg yolk with some sauce and stir into the sauce. Put the vanilla sauce in a cool place. Serve the rhubarb groats with the vanilla sauce and decorate with mint
waiting time approx. 2 hours