For the filling: Cut the apples into 1/4-inch slices and place them in a large bowl. Toss with the lemon juice to keep them from browning. Add the brown sugar, cornstarch, Warm Spice Blend, kosher salt and cinnamon and toss to combine. Mix in the boiled cider syrup and vanilla. Cover the mixture and let it sit at room temperature while you make the pie dough.
For the pie dough: Add the flour, granulated sugar and kosher salt to a food processor and pulse to combine. Add the butter and pulse to incorporate so that about three-quarters of the mixture is mealy and the rest has some slightly larger, pea-sized bits of butter. Combine the ice water and cider vinegar in a measuring cup. Drizzle the water and vinegar into the food processor and continue to pulse just until the mixture comes together to form a dough. If it seems dry or is having a hard time coming together, add a bit more water, a few drops at a time, until it comes together.
Turn the dough out onto a clean surface and use your hands to press on any stray crumbs. Divide the dough in half, then divide one of the halves in half again so that you have 3 pieces of dough. Pat each piece into a disc and wrap in plastic wrap. Refrigerate for at least 30 minutes or until ready to roll out for the pie.
For the assembly: Flour a work surface and roll out the largest disc of dough into a circle just larger than 12 inches. Place it in a 9-inch pie plate and refrigerate. Roll out the 2 remaining dough discs to about 10 inches each. Cut the dough into 2-inch-wide strips for making a lattice top. Set the strips aside.
Position an oven rack in the lower third of the oven (with a pizza stone if you have one) and preheat to 400 degrees F.
Fill the pie crust with the apples (it will seem like a lot but they bake down!) and pour the juices over it. Distribute the butter over the top. Weave the dough strips together over and under to form a lattice crust over the top. Pinch the edges to seal, trim, fold the edges over and crimp. Give the edges a little hug to make sure they are sitting snugly on the rim of the pie plate; otherwise they could fall off in the oven. Freeze the pie for 15 minutes.
Brush the lattice with the egg wash, then sprinkle with the turbinado sugar and flaky salt. Place the pie on a baking sheet and bake until the internal temperature reaches 195 degrees F, 45 to 55 minutes. Let cool slightly.
Serve the pie with large dollops of whipped cream.
Warm Spice Blend:
Yield:scant 3 tablespoons
Layer the cardamom, ginger, cinnamon, cloves and nutmeg in a medium glass jar and tighten the lid. Shake to combine. Keep on hand to add to your favorite desserts and beverages -- or just toast with butter!