Mix pudding powder and sour cream with the whisk of the hand mixer. Add 125 g sugar, vanillin sugar and eggs and stir in. Then add milk. Coarsely crumble the rusks.
Wash and peel apples, cut out the core. Dice apples roughly. Grease an ovenproof dish (2 litres capacity), (put 1 tablespoon of rusk aside) put the rest of the rusk into the dish, spread apple pieces evenly on top.
Pour the vanilla-egg glaze on top and bake in the preheated oven (electric: 200 °C/ gas: level 3) for 50-55 minutes. In the meantime, mix remaining sugar, cinnamon, flaked almonds and remaining rusk.
Sprinkle evenly over the casserole 15 minutes before the end of the baking time. Serve the casserole decorated as desired with a slice of apple and lemon balm.