Bitman's recipe uses homemade puff pastry - "1/2 recipe" of it - and would make twelve 6" squares once it was rolled out. I used one half of the box - one piece - and it made six 6" squares after I rolled it out. Therefore I used half of the apples and other ingredients.
I used two Granny Smith apples, and added some raisins since I like raisins in my apple turnovers.
The recipe said to bake these for 40 minutes, but they were well-done at 35. If I'd waited until 40 they would have been burned. What DID happen, which isn't mentioned in the original recipe, is that a lot of juice came out of the turnovers and burned on the bottom of the cookie sheet. Luckily it didn't cause the turnovers to burn.
adapted from Mark Bitman's How to Cook Everything
2 tart apples, peeled and cored
1/2 tablespoon lemon juice
1/2 tablespoon cornstarch
1/2 teaspoon minced or grated lemon zest, or more to taste
1/2 teaspoon ground cinnamon, or more to taste
1/4 cup sugar, or more to taste, plus more for the work surface and for sprinkling
1/2 of a package of puff pastry (1 sheet), thawed
Grate the apples in a food processor or on the coarse side of a box grater. Immediately toss them with the lemon juice. Add the cornstarch, lemon zest, cinnamon, and sugar. Taste and add more lemon zest or cinnamon if you like.
Use sugar to coat a work surface. Roll out the pastry sheet, sprinkling with sugar as you work, until the dough is less than 1/4" thick and measures approximately 15" x 10". Cut 5" squares of pastry. Sprinkle lightly with sugar. Place on a lightly greased cookie sheet.
Divide the filling evenly among the six squares; fold over the edges to form a triangle. Juices will be escaping - use them to help seal the edges. I had to even blot up a lot of juice with paper towels. Slash the top of the turnover with a sharp knife once or twice so steam can escape. Chill while you heat the oven or for up to several hours
Heat the oven to 350˚. Brush the tops of the turnovers with a little water and sprinkle with sugar. Bake until the turnovers are golden brown, about 33 minutes. Serve warm or at room temperature. Makes 6.