For the apple pockets, peel the apples.
If desired, unpeeled apples can also be used. Remove the skin. Preheat the oven to 180 °C with circulating air and take the puff pastry out of the packaging.
First quarter the apples and then cut them into cubes of about 1 cm, put them in a bowl and mix them with the lemon juice and zest. Add the cinnamon, sugar, nutmeg (a little) and flour and mix everything together.
Cut the puff pastry into 3 equal parts and divide the mixture evenly among the 3 parts. Brush the edges with the egg yolk (or water) and fold in to form pockets. Fold the edge up and brush the apple pockets with the egg yolk. Use a knife to cut small holes in the top of the apple pouches (to allow moisture to escape) and place on a baking sheet in the oven for about 20 to 25 minutes at 180 °C on the middle rack.
Allow to cool and serve the apple pockets.