For the batter, stir the softened butter / margarine until creamy. Mix the sugar with the vanilla sugar and stir in. Stir until a bound mass has formed. Mix in the eggs one by one. Mix the almonds / hazelnuts, cinnamon, salt, flour and baking powder and stir into the sugar-egg mixture. Spread the dough on a greased, mottled baking sheet.
For the pudding cream, stir the pudding powder with 2 tablespoons of sugar, 4 tablespoons of the milk and 2 egg yolks until smooth, bring the rest of the milk to the boil. Stir in the mixed pudding and egg mixture, bring to the boil briefly, transfer to a bowl and allow to cool. Beat the 2 egg whites until stiff and fold into the cooled pudding mixture. Spread the pudding cream evenly on the dough.
Place the plums on the pudding cream and sprinkle with a mixture of sugar and cinnamon (if the plums are very sweet, you can do without them).
For the crumble, put the flour, sugar and almonds in a mixing bowl. Add the cold butter / margarine cut into pieces and work into fine crumble. Distribute on it.
Bake in a preheated oven at 180 ° C top / bottom heat for about 45-50 minutes. Make a chopstick test.