Cut the apple into bite-sized chunks. Soak in salted water. If you cut them in different sizes, the filling will have a nice texture.
Put a small amount of oil in a pot, and cook the apples over medium heat, being careful not to let them burn.
When the apples are somewhat translucent, lower the heat and add the sugar, cinnamon and 100 ml water. Simmer for about 10 minutes until they are golden brown.
When it looks like this photo, taste and adjust the flavor by adding sugar or cinnamon.
Add 50 ml water to prevent it from burning, and simmer for 5 more minutes. Cook until the added water evaporates. Remove from heat and add the lemon juice.
Addendum: I used to put the puff pastry sheets directly on the oven tray, but some people said they stuck to the pan after baking, so I've made some changes!
Leave the puff pastry sheets at room temperature for 15 minutes. Place 2 sheets of puff pastry on a parchment paper-lined baking pan. Put the apple filling on after it has cooled somewhat.
Don't put too much on, and leave the edges free of filling. When it's spread evenly, add 2-3 shakes of cinnamon.
Make deep lengthwise cuts with a knife in the two remaining sheets. Place these on top of the apple filling topped sheets from Step 7. At this point, preheat the oven.
Press the back of a fork along the edges to close. If the puff pastry is hard, the edges may not stick together well, like the one in the background in the photo.
Glaze by brushing with egg wash made with an egg yolk beaten with 1 teaspoon of water.
Bake in the upper rack of the oven at 200℃ for 10 minutes. When the surface starts to brown, lower the heat to 170℃ and bake for 10 more minutes.
Every oven is different, so please adjust the baking time according to your oven while keeping an eye on it.
It's ready when it has puffed up and the surface is golden brown. Take it off the pan and cool.
Done! These are good either piping hot, or cold.
This time I used puff pastry that already had air holes in it. If using puff pastry without holes, poke holes in the four sheets with a fork (see photo in Step 10).
How about spreading the leftover apple filling on top of toast or English muffins for breakfast?
Story Behind this Recipe
You may have seen a recipe like this a long time ago, but this is the apple pie my mother used to make when I was a child. Now it's what I like to make for my own family.
Basically, it's foolproof, since you use frozen puff pastry. If I were to suggest anything, it would be to make sure the apple filling isn't watery, and not to put too much in or it will leak out. If it leaks out, it will burn and the pastry won't puff.