Peel, core, and slice all your apples about 1/4 inch thick. Try to keep the slices uniform so they cook evenly. Place them in a large bowl and add the brown sugar, flour, cinnamon, nutmeg, salt, lemon juice, and vanilla extract. Toss everything together until every apple slice is coated. Set the bowl aside for 10 minutes. The apples will start to release some juice and the sugar will begin to dissolve.

Lightly flour your counter and roll out one disc of pie dough into a circle about 12 inches across. Drape it into a 9-inch pie dish and press it gently into the bottom and up the sides. Let any excess hang over the edge. Refrigerate while you roll out the second disc for the lattice.

Roll the second disc of dough into a circle about 12 inches across. Using a sharp knife or pastry wheel, cut the dough into strips about 1 inch wide. You will need 8 to 10 strips. Place the strips on a cutting board or parchment and refrigerate them while you fill the pie.

Pour the apple filling into the chilled bottom crust, mounding it slightly in the center since the apples will settle as they bake. Scatter the small pieces of butter over the top of the apples.

Lay half of your dough strips parallel across the filling, spacing them evenly. Fold back every other strip halfway. Lay one strip perpendicular across the unfolded strips. Unfold the folded strips back over the perpendicular one. Now fold back the strips that were not folded before and lay another perpendicular strip. Repeat this weaving until the lattice covers the whole pie. If the dough gets soft and sticky, slide the pie into the refrigerator for 10 minutes to firm up before continuing.

Trim any overhanging dough to about 1 inch beyond the rim of the dish. Press the bottom crust and lattice ends together, then fold and crimp the edge all the way around. Place the assembled pie in the refrigerator for 20 minutes. Preheat your oven to 375 degrees F and place a foil-lined baking sheet on the rack below where the pie will sit to catch any drips.

Brush the chilled lattice and crimped edge with the egg wash using a pastry brush, covering everything evenly. Sprinkle granulated sugar over the top. Place the pie on the middle rack of the oven with the foil-lined sheet below it.

Bake for 55 to 60 minutes. The pie is done when the filling is actively bubbling through the lattice openings and the crust is a deep, even golden brown. If the crust edges are browning too fast before the 50-minute mark, tent them loosely with strips of foil. Do not pull the pie early. You want to see real bubbling in the center, not just at the edges, to know the filling is fully cooked and thickened.

Transfer the pie to a wire rack and let it cool for at least 2 hours before slicing. This waiting time is not optional. The filling needs to set so it slices cleanly instead of running out the sides. Serve with vanilla ice cream or a spoonful of lightly whipped cream.