Preparation Steps

• Make the crust: In a large bowl, whisk together 2 cups of flour, 1 tablespoon sugar, and 1 teaspoon salt. Cut in cold butter using a pastry cutter or fork until mixture resembles coarse crumbs.
• Add ice water, a tablespoon at a time, mixing until the dough just comes together. Divide the dough into two discs, wrap in plastic, and chill for at least 30 minutes.
• Prepare the filling: In a large bowl combine sliced apples, 0.75 cup granulated sugar, 0.25 cup brown sugar, 2 tablespoons cornstarch, 2 tablespoons lemon juice, 1 teaspoon cinnamon, and 0.25 teaspoon nutmeg. Toss until apples are evenly coated.
• Preheat the oven to 375°F (190°C). Line a 13x9-inch baking sheet with parchment paper and lightly flour the surface.
• Roll out one dough disc to a rectangle slightly larger than the baking sheet. Transfer to the prepared sheet. Spoon apple filling into center, spreading evenly and leaving a 1-inch border.
• Roll out second dough disc to cover the apples. Place over filling and fold edges under, crimping to seal. Cut a few vents in the top to allow steam to escape.
• Brush the top with beaten egg mixed with 1 tablespoon milk and sprinkle coarse sugar over the surface.
• Bake for 40 to 45 minutes, or until crust is golden brown and filling is bubbling. If edges brown too quickly, tent with foil.
• Cool the slab pie on a wire rack for at least 30 minutes before slicing into squares. Serve warm or at room temperature, optionally with vanilla ice cream or whipped cream.