1 pound Granny Smith apples (about 2-1/2 medium)
2 teaspoons fresh lemon juice
2/3 cup packed light brown sugar
1/4 cup plus 1 tablespoon granulated sugar
3 tablespoons cornstarch
1/2 teaspoon ground cinnamon; more to taste
1/4 teaspoon kosher salt
1/8 teaspoon ground nutmeg
1 large egg white
2 teaspoons unsalted butter, softened, plus 1 tablespoon cold unsalted butter, cut into small (1/4-inch) cubes
4 to 6 tablespoons all-purpose flour
2 refrigerated piecrusts (or make your own with the Flaky Pie Pastry recipe at the bottom of the page) directions Position two oven racks in the lower third of the oven and heat the oven to 400 degrees F.
To make the filling: Peel the apples, cut each in half from top to bottom, remove the cores with a melon baller, and trim the ends with a paring knife. Lay the apples, cut side down, on a cutting board. Cut the Cortland apples crosswise into 3/4-inch pieces, and then halve each piece diagonally. Cut the Granny Smith apples crosswise into 1/4-inch slices, leaving them whole. Put the apples in a large bowl and toss with the lemon juice.
Combine the brown sugar, 1/4 cup of the granulated sugar, the cornstarch, cinnamon, kosher salt, and nutmeg in a small bowl. (Don't add this to the fruit yet.)
In a small dish, lightly beat the egg white with 1 teaspoon water. Set aside.
Assemble the pie: Butter a 9-inch ovenproof glass (Pyrex) pie plate, including the rim, with the 2 teaspoons of softened butter.
Rub 2 to 3 tablespoons of flour into the surface of a pastry cloth, forming a circle about 15 inches across, and also into a rolling pin stocking. If you don't have a pastry cloth, rub the flour into a large, smooth-weave, cotton kitchen towel and use a floured rolling pin. Roll one of the disks of dough into a circle that's 1/8 inch thick and about 15 inches across.
Lay the rolling pin across the upper third of the dough circle; lift the pastry cloth to gently drape