In a large mixing bowl, combine the all-purpose flour, granulated sugar, and salt. Cut in the unsalted butter until the mixture resembles coarse crumbs.

Add Ice Water

Gradually add the ice water, one tablespoon at a time, mixing until the dough comes together. Be careful not to overwork the dough.

Chill the Dough

Divide the dough into two equal portions, shape into discs, wrap in plastic wrap, and refrigerate for at least 1 hour.

Filling Preparation

Prepare the Apples

In a large bowl, toss the sliced apples with granulated sugar, ground cinnamon, lemon juice, cornstarch, and vanilla extract until well combined.

Let the Filling Rest

Let the apple mixture sit for about 15 minutes to allow the juices to release.

Assembling and Baking

Preheat the Oven

Preheat your oven to 425°F (220°C).

Roll out the Dough

On a floured surface, roll out one disc of dough to fit a 9-inch pie pan. Place it in the pan and fill with the apple mixture.

Create the Lattice Top

Roll out the second disc of dough and cut it into strips. Arrange the strips in a lattice pattern over the apple filling, weaving them over and under each other.

Prepare the Egg Wash

In a small bowl, whisk together the egg and milk. Brush the egg wash over the lattice crust for a golden finish.

Bake the Pie

Bake in the preheated oven for 45-50 minutes or until the crust is golden brown and the apples are bubbly.

Cool and Serve

Allow the pie to cool for at least 30 minutes before slicing. Serve warm with ice cream or whipped cream if desired.