Prepare the Oven and Apples: Preheat your oven to 425°F (220°C). Wash, peel, core, and thinly slice the apples. Place them in a large mixing bowl and set aside. Preparing the apples first ensures they’re ready to go once your caramel mixture is hot and bubbling.
Make the Caramel Filling: In a medium saucepan, melt the butter over medium heat until fully liquefied. Whisk in the flour to create a smooth paste, cooking for about 1–2 minutes until it turns slightly golden and aromatic. Stir in the granulated sugar, brown sugar, and water, whisking constantly. Allow the mixture to reach a gentle boil, then reduce the heat to low and let it simmer for 3–5 minutes, forming a glossy caramel-like sauce. Remove from heat.
Prepare the Pie Crust Base: Line a 9-inch pie dish with one of the pastry sheets, gently pressing it into the bottom and up the sides. Roll out the second sheet of pastry slightly larger than the pie dish and cut it into eight even strips, approximately 1 inch wide, to create the lattice topping later.
Assemble the Filling: Evenly arrange the apple slices in the prepared bottom crust, slightly mounding them toward the center. The layers of apples should be snug, with minimal gaps for the best texture and flavor.
Create the Lattice Top: Lay four pastry strips vertically over the apples, spacing them evenly. Fold back every other strip halfway, place one of the remaining strips horizontally across, then fold the vertical strips back over. Repeat this weaving process until all strips form a classic lattice pattern. Trim any overhanging dough, then pinch and crimp the edges to seal.
Add the Caramel Glaze: Slowly pour the warm sugar-butter mixture over the lattice crust, ensuring it seeps down into the apples and lightly coats the top. Use a pastry brush to spread the glaze evenly, avoiding spills on the pan edges to prevent burning.
Bake to Perfection: Place the pie in the preheated oven and bake for 15 minutes. Lower the oven temperature to 350°F (175°C) and continue baking for 35–45 minutes, or until the apples are tender and the crust is golden brown. Allow the pie to cool slightly before serving to let the filling set.