Ingredients :

• The apples — Take at least two varieties—a Golden or Fuji for melting sweetness, a Granny Smith for acidity and holding up during baking. Avoid mealy varieties like Reinette: they turn into mush and you lose all texture. A kilo seems like a lot, but it reduces well.
• Cold butter — Cold, really cold. Straight out of the refrigerator just before using, cut into small cubes. This is what creates small pockets of steam in the dough during baking—those famous crispy layers. If the butter softens along the way, the result will be compact rather than flaky.
• Cinnamon — One teaspoon, no more. The cinnamon should fragrance, not dominate. If you have freshly ground cinnamon, it’s significantly more intense—you can then reduce to three-quarters of a spoon.
• Cornstarch — Prefer cornstarch over flour if you have it. It binds the apple juices during baking without making the filling heavy. Flour also works but gives a slightly more opaque and stickier result.