Buttermilk Crusted Apple Pie

Buttermilk Pie Crust:

Cube the 2 sticks of unsalted butter and measure out the buttermilk then freeze both for 10 minutes.

In a large bowl, combine the flour, sugar, and salt, fluffing with a fork to aerate. Add the cold butter and cut it into the flour mixture with a pastry cutter or your fingers until the butter is about the size of peas. This can also be done in a food processor but be very judicious.

Pour in 1/2 cup of buttermilk (and optional vinegar) and stir with a fork until it starts to come together. It will be quite loose. Grab a small amount of the mixture and pinch it together; if it doesn't hold together, add a tablespoon more buttermilk and stir. Repeat until the dough holds together lightly but enough.

Lightly flour a work surface and dump the crust dough out onto it. Push the dough together and knead a couple times until it forms into mostly a ball then cut it in half. Wrap each half in plastic wrap and form the dough into disks then chill in the refrigerator for at minimum 1 hour, up to 3 days.

Apples:

Peel and slice the apples about 1/4" thick, adding them to a large bowl with the optional lemon juice, light brown sugar, granulated sugar, cinnamon, nutmeg, and salt. Toss well to coat and leave on the counter to macerate for at minimum 30 minutes, up to 3 hours.

Drain the apples through a strainer, collecting the liquids. It should amount to at least 1/2 cup. Return the apples to the bowl and toss them with the cornstarch until no longer visible.

Remove the pie crusts from the refrigerator and allow about 10 minutes for the chill to come off.

Pour the collected liquid into a small saucepan, add the 2 tablespoons of butter, and boil until it reduces to about 1/3 cup, thickened and syrupy. Swirl but avoid stirring.

Pour the now reduced liquid over the apples and toss to coat.

Assembly:

Lightly flour a work surface and roll out one disk of dough for the bottom crust to about 12" in diameter or about 1/8" thick. Roll the dough around the rolling pin to move it easily and set it into the pie dish.

Pour the apple mixture into the pie crust and roll out the second disk of dough to about 12" in diameter. Create a design with the vent holes as desired.

Dampen the edge of the bottom crust with a little water, set the top crust atop it, tuck the top crust under and behind, between the top crust edge and the pie dish then crimp together.

Cover the pie with plastic wrap and chill in the refrigerator for 1 hour.

Bake:

Place an oven rack on its lowest position in the oven and set a baking stone atop it or an upside down baking sheet. Begin preheating the oven about 30 minutes before removing the pie from the refrigerator to 425 F (218 C). Spray a piece of aluminum foil lightly with cooking spray and set it spray side up on the stone/sheet.

Whisk the 1 egg and water together and wash the top of the pie with it or the heavy cream; this is an optional step. Bake the pie atop the stone/sheet for 45-55 minutes, until juices are bubbling and the crust is nicely browned. If the crust edges or the pie itself are browning too quickly, cover with foil.

Once baked, let the pie cool on a rack for at minimum 4 hours so it can set properly. Serve as desired.