A century-old Gravenstein tree provides the apples for Linda Styger's pie; it's one of several fruit trees on the Organic Valley dairy farm that Styger and her family operate in Washington State. Her "flat pie" is a large, rectangular affair which can be cut into squares and eaten by hand, and Linda often makes two restaurant-size pans of it--"one to eat and one to give away"—or even up to four or six at a time, so that she can freeze some for future enjoyment. We've converted her recipe to use a 10-by-15-inch pan, still big enough to yield 12 to 16 servings.
Linda's Gravensteins are very large and sweet, so you don't need many and they don't need very much sugar. They cook into a thick, chunky mass that firms up between the crusts, making it possible to do what Linda's family does: "Walk outside with a piece in your hand and enjoy it outdoors." Feel free to use your own favorite pie apple—and to adjust the sweetener as desired.
Heat the oven to 425 degrees. To make pie dough: You can use a pastry cutter to cut the butter into the flour by hand, or use the pulse button on food processor or stand-up mixer. Place the flour in the bowl and cut in the butter until mixture resembles cornmeal in texture. Sprinkle ice a tablespoon at a time over the mixture while tossing mixture with a large fork. Add only enough water—12 to 13 tablespoons total--to bring the mixture together into a loose dough. Briefly work the dough with your fingers and gather it into a ball.
Divide dough in half and place on lightly floured surface. Using a little flour if necessary to prevent sticking, roll out half the dough to a rectangle that’s about 11 by 15 inches. Use a metal spatula to loosen the dough from the work surface. Fold the dough into quarters, transfer it to a 10-by-15-inch jelly roll pan (that’s a baking sheet with sides) and unfold, lightly pressing the dough to fit the bottom of the pan and up its sides.
To prepare apples: peel and slice them into a medium thickness. You should have about 6 cups total (but you can use more if you’d like).
To fill and bake pie: Sprinkle cornflakes evenly over bottom crust. Spread apple slices over cornflakes. Sprinkle sugar evenly over apples. Sprinkle cinnamon evenly over sugar. Roll out remaining dough to fit over the apples. Press and/or crimp the edges of the bottom and top crusts together. Make one or two slits in the top crust. Bake at 425 degrees for 15 minutes, then reduce oven heat to 375 degrees and continue baking until crust is firm and golden and apples are tender when pierced with a fork, about 45 minutes longer.
Let pie cool off 10-15 minutes. Meanwhile, make a glaze: Place powdered sugar in a two-cup glass measuring cup (the kind with a spout). Beat in just enough milk to make a thin glaze. While pie is still warm, drizzle the glaze evenly over the top crust in a back-and-forth pattern. Serve pie warm with vanilla ice cream on serving plates or let it come to room temperature and eat slices of it out of hand.