How to Make It
Preheat oven to 375°F. Roll 1 dough into a 13-inch circle on a floured surface; fit into a 9-inch pie plate coated with cooking spray. Chill until ready to use.
Heat sugar, butter, 1 tablespoon water, and salt in a skillet over medium-high; cook 1 minute, stirring constantly. Stir in milk and vanilla. Bring to a boil, and cook, stirring constantly, until thickened, about 1 minute. Remove from heat; let stand 10 minutes.
Combine grated apple and 1 tablespoon flour in a bowl. Add apple wedges and remaining 3 tablespoons flour; toss to coat. Pour sugar mixture over apples; toss. Nestle apple mixture into piecrust in pie plate.
Roll remaining pie dough into an 11 1/2-inch circle on floured surface. Place over apples in pie plate. Fold dough edge under, flute edges, and trim off any excess. Brush egg white over crust. Cut 6 to 8 (1-inch-long) slits in crust. Bake on bottom rack at 375°F for 1 hour or until browned and bubbling. Tent with foil after 40 minutes to prevent overbrowning, if needed. Remove from oven; cool on a wire rack. Cut pie into 10 wedges.