Step 1: Prepare the Pie Dough

1. In a mixing bowl, combine flour and salt.
2. Cut in the cold butter using a pastry cutter or fork until the mixture resembles coarse crumbs.
3. Gradually add ice water, 1 tablespoon at a time, mixing until the dough comes together.
4. Form the dough into a small disc, wrap it in plastic, and refrigerate for at least 30 minutes.

Step 2: Make the Apple Filling

1. Peel, core, and dice the apple into small cubes.
2. In a bowl, mix the apple pieces with sugar, cinnamon, nutmeg, lemon juice, vanilla extract, and cornstarch.
3. Let the mixture sit for 5-10 minutes to allow the flavors to develop.

Step 3: Roll Out the Dough & Assemble the Pie

1. Preheat the oven to 375°F (190°C).
2. Roll out the chilled dough on a floured surface to about 1/8-inch thickness.
3. Cut a circle slightly larger than your pie dish and press it gently into the dish.
4. Fill the crust with the prepared apple mixture and dot with small butter pieces.
5. Roll out the remaining dough and either cover the pie completely or create a lattice top.
6. Seal the edges by crimping with a fork and brush with egg wash for a golden finish.

Step 4: Bake the Pie

1. Place the pie on a baking sheet to catch any drips.
2. Bake for 25-30 minutes, or until the crust is golden brown and the filling is bubbling.
3. Let the pie cool for 10-15 minutes before serving.