Heat 1,500 ml milk (room temperature) in a small saucepan. Remove the pulp from the vanilla pod and heat it with the rest of the vanilla pod in the milk. Caramelize 100g sugar in a pan with a sip of water. Peel the rhubarb and chop into pieces (keep the skin). Mix 4 egg yolks and 120g sugar in a bowl. Add the boiled vanilla milk to the egg and sugar mixture while stirring. Preheat the oven to 170 degrees. Deglaze the caramel with red wine and apple juice and then reduce the rhubarb peels in it. Meanwhile, for the crumble, stir together 160g flour, 100g sugar, 100g butter (room temperature), a pinch of salt and a whole egg.