Grease a springform pan (26 cm Ø). Knead flour, brittle, 200 g sugar, vanillin sugar, 1 pinch of salt, 225 g butter in flakes and 1 egg first with the dough hooks of the hand mixer and then briefly with your hands to form crumbles
Spread half of the crumble as a base in the mould and press on. Sprinkle with ground hazelnuts
Peel, quarter, core and cut apples into thin slices. Sprinkle with lemon juice and spread on the crumble base
Mix sour cream, 4 eggs, 75 g sugar and sauce powder and pour over the apples. Sprinkle the remaining crumbles on top
Bake in the preheated oven (electric oven: 200 °C/circulating air: 175 °C/gas: level 3) on the lowest rack (gas: see oven manufacturer) for approx. 50 minutes. Leave to cool in the mould. Dust with icing sugar before serving. Whipped cream tastes good with it