2 tablespoons unsalted butter
2/3 cup (packed) light brown sugar
3 tablespoons tapioca flour (aka starch)
1 1/2 teaspoons ground cinnamon
1 pinch kosher salt
• Egg wash:
1 egg
1 tablespoon heavy cream
1 pinch kosher salt
Parbake: Adjust oven rack to the lower-middle position and heat to 350 degrees. Line the chilled pastry with foil, draping it loosely over edges. Fill with granulated sugar (alternatively, use baking beans). Set on a baking sheet. Bake until pastry is set and golden, about 1 hour. Lift out the foil. If pale, continue baking until lightly colored, 5-10 minutes. Let cool. Roasted sugar can replace granulated sugar in other recipes; it offers a hint of caramel flavor. Cool, seal and store.
Wilt: Peel, core, halve and slice apples crosswise into 1/4-inch thick half-circles. (An apple peeler contraption makes quick work of the job.) In a wide skillet, melt butter over medium heat. Slide in apples and toss to coat. Cover and cook, stirring regularly, until apples lose their snap, about 7 minutes. Uncover and stir in brown sugar, tapioca, cinnamon and salt. Cook until syrup begins to thicken, 1 minute. Let cool.
Fill: Scrape cooled apples into cooled pie shell. Drape the top pastry over apples, trim edge to 3/4-inch overhang. Fold the overhang under itself, covering the parbaked edges (no need to unite baked and unbaked pastry, they will join forces in the oven). Chill firm, 30 minutes
Bake: With rack still in lower-middle position, heat oven to 400 degrees. Whisk together egg wash, and brush over chilled pie. Cut in a starburst of vent slits. Set pie on a parchment-lined baking sheet. Bake until top is golden brown, center is bubbly and 195 degrees, about 1 hour. (Pull out pie before it reaches 200, warns Parks. That’s when apples break down to mush.) If top is browning too quickly, cover loosely with foil. Cool at least 1 hour before serving. To restore crisp crust later, reheat at 350 for 10 minutes.
