Put flour, sugar, vanilla sugar, salt and egg yolk in a bowl. Add butter in pieces and 1 tablespoon of cold water. Knead to a smooth dough. Wrap in foil and chill for about 30 minutes.
In the meantime peel the apples, quarter them and cut out the core. Cut the apple quarters into narrow slices and sprinkle with lemon juice. Roll out dough thinly on a lightly floured work surface and cut out 3 circles (14 cm Ø).
Knead dough remains together and roll out to the 4th circle. Line 4 greased, breadcrumbed tartlet moulds with lift-off base (approx. 12 cm Ø) with it. Prick the bases several times with a fork and sprinkle some breadcrumbs over them.
Spread apple slices in it. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 20-25 minutes. Coat with warmed jelly, sprinkle almond flakes on the edges and bake in the preheated oven (electric range: 225 °C/ convection oven: 200 °C/ gas: level 4) for 5-8 minutes.
Let the tartlets rest in the mould for 5-10 minutes. Remove from the mould and allow to cool completely. Serve dusted with icing sugar.