Sift the flour into a large bowl. Add yeast, sugar and a pinch of salt. Add milk and butter and knead with the dough hook of the food processor to a smooth dough.
Cover and let it rise for 1 hour.
In the meantime halve the plums and stone.
Put all crumble ingredients in a bowl and knead with your hands or hand mixer to a crumbly dough. Set aside.
When the yeast dough has gone. Set the oven to 180 degrees.
Grease a tart mold or cover it with baking paper. Briefly knead yeast dough on a floured surface and then roll out. Place in the mold and press down, cover with the plum halves close and dense.
Sprinkle the cover with Crumbles and bake for 25 minutes. The plums should be soft and bubbling and the Crumbles are golden brown. If necessary bake 10 Minutes more and cover the Cake with baking paper. Let cool down.