Wash and clean the rhubarb and cut into 2 cm pieces. Mix the rhubarb and sugar in a bowl, cover and leave to stand for about 1 hour. Mix flour, butter, egg yolk and cane sugar to crumbles.
Chill the crumbles for about 1 hour.
Wash and clean the strawberries and, depending on size, cut them in half or quarters. Mix the rhubarb, vanilla sugar and strawberries and place in one large or 4 small ovenproof moulds. Spread crumbles over them and bake in a preheated oven (electric cooker: 200 °C/ circulating air: 175 °C/ gas: see
manufacturer) bake for about 30 minutes. Serve lukewarm.