Step 1: Prepare the apple filling. In a large bowl, combine the sliced apples, granulated sugar, all-purpose flour, ground cinnamon, ground nutmeg, and lemon juice. Toss gently until the apples are evenly coated. Let the mixture sit for 10-15 minutes to allow the apples to release some of their juices.

Step 2: Assemble the pie. Preheat your oven to 425°F (220°C). Carefully unroll one store-bought pie crust and fit it into a 9-inch pie dish, pressing it gently against the bottom and sides. Pour the apple filling into the crust, mounding it slightly in the center. Dot the top of the filling with the small pieces of butter. Place the second store-bought pie crust over the filling. Trim the edges of both crusts, leaving about a 1/2-inch overhang. Crimp the edges together to seal, creating a rustic, home-baked appeal that will contribute to the crust's final textured look.

Step 3: Finish and glaze the crust. Cut several small slits or decorative vents into the top crust to allow steam to escape during baking. In a small bowl, whisk the large egg with 1 tablespoon of water to create an egg wash. Brush the entire top surface of the pie crust generously with the egg wash; this will contribute to the subtle shimmer and the magnificent, unevenly distributed toasted golden-brown hue as seen in our hero photo.

Step 4: Bake for a 'shattered-glass flaky' result. Place the pie on a baking sheet to catch any drips. Bake for 20 minutes at 425°F (220°C). After 20 minutes, reduce the oven temperature to 375°F (190°C) and continue baking for another 35-40 minutes, or until the crust boasts a deep, caramelized amber on its ridges and the surface reaches a rich, golden-brown hue, indicative of a distinctly 'shattered-glass flaky' texture. The filling should be bubbling thickly, and a thin knife inserted into a vent should easily pierce the tender apples.

Step 5: Cool the pie. Once baked to perfection, remove the pie from the oven and place it on a wire rack. Allow it to cool completely for at least 3-4 hours before slicing and serving. This resting period is crucial for the filling to set properly, ensuring a clean slice and a perfectly moist interior.