Apple Slab Pie

1. Prepare the Crust:

1. In a large bowl, combine flour and salt.
2. Cut in cold butter using a pastry cutter or fork until the mixture resembles coarse crumbs.
3. Gradually add ice water, 1 tbsp at a time, mixing until the dough just comes together.
4. Divide the dough in half, shape into discs, wrap in plastic, and chill for at least 30 minutes.

2. Prepare the Filling:

1. In a large bowl, combine apple slices, sugars, cinnamon, nutmeg, cornstarch, and lemon juice. Toss to coat evenly.

3. Assemble the Pie:

1. Preheat the oven to 375°F (190°C). Grease a 9×13-inch baking pan.
2. Roll out one dough disc on a floured surface to fit the bottom of the pan. Place it in the pan, pressing into the edges.
3. Pour the apple filling over the crust, spreading it evenly. Dot with butter cubes.
4. Roll out the second dough disc and place it over the filling. Seal and crimp the edges.
5. Brush the top crust with the beaten egg and sprinkle with coarse sugar if desired.

4. Bake the Pie:

1. Cut slits in the top crust for ventilation.
2. Bake in the preheated oven for 40-45 minutes, or until the crust is golden brown and the filling is bubbling.
3. Cool slightly before slicing into bars.