Thaw the puff pastry sheets a little. Mix the Nutella with the hazelnuts and spread about 1 tablespoon on each plate.
Wash and core the apple, cut into small pieces and mix with the cinnamon sugar. Spread on the pastry sheets.
Fold the puff pastry into pockets and press the edges together with a fork. Brush with egg yolk, place on a baking sheet and bake in a preheated oven at 180 ° for about 25 minutes.