Wash the plums, drain, halve and stone them. For the crumbles, put flour, fat in flakes, sugar, salt, vanillin sugar, cinnamon, egg yolk, baking powder and 4 tablespoons of cold water in a large mixing bowl.
Mix with the dough hooks of the hand mixer. Then work into crumbles with your hands. Spread a good 2/3 of the crumbles onto a greased baking sheet
Carefully spread with plum jam. Spread the plums on top and sprinkle the remaining crumbles evenly over it. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 45 minutes.
Remove from the oven, place on a cake rack and allow to cool.