For the dough, put the flour, poppy seeds, sugar, baking powder, vanilla sugar and salt in a bowl. Measure the liquid ingredients in a measuring cup and stir. Add to the dry ingredients and stir with a whisk.
For the marzipan cream, bring the soy milk to the boil with a pinch of salt. Add the marzipan and crush it with a fork. Stir vigorously until the marzipan has dissolved. Stir in the starch and bring to the boil again.
For the crumble, knead the ingredients into crumble with your hands.
Grease a 26-inch springform pan and add the batter first. Then spread the cream on it like a cow stain. Spread the plums on top and top with sprinkles. Bake at 180 degrees for about 40 minutes and allow to cool.