Preheat the oven to 180 ° C (top / bottom heat). For the dough, mix all the ingredients together and distribute them evenly on a baking sheet lined with baking paper.
Wash the plums or plums, cut them in half, remove the seeds and spread them on the dough in a flake shape. Then make the crumble from butter, sugar, vanilla sugar and flour and spread on the fruit.
Bake for 35 minutes. Then let the cake cool down and enjoy with whipped cream if necessary.