Place the 3 cups of flour, 1 tablespoon of sugar, and 1 teaspoon of kosher salt into the bowl of a high-capacity food processor. Pulse a few times to aerate and mix.

Add the chilled butter cubes and the cold vegetable shortening directly over the dry ingredients. Pulse 8 to 12 times, strictly until the fats are cut into the flour and the mixture resembles coarse, pea-sized crumbs. (Preserving these cold lipid pockets is critical for a flaky crust).

With the machine running, slowly pour the ½ cup of ice water down the feed tube. Pulse just until the dough begins to clump together into a ball. Do not overprocess.

Turn the dough out onto a heavily floured board. Divide it evenly into two round disks, wrap each tightly in plastic wrap, and refrigerate for exactly 30 minutes to relax the gluten and solidify the fats.

Bring a large pot of water to a rolling boil over high heat. Prepare a separate large bowl filled with ice water.

Carefully drop 2 to 3 peaches at a time into the boiling water for exactly 10 to 12 seconds to loosen the skins.

Use a slotted spoon or spider to immediately transfer the peaches to the ice water bath to halt the cooking process. Once cooled, use a sharp paring knife to effortlessly peel the soft skins away.

Halve, pit, and slice the peeled peaches to a uniform ¼-inch thickness. Place the slices into a large mixing bowl and toss gently with the fresh lemon juice to prevent oxidation.

Preheat the oven to 400°F.

In a small ceramic bowl, whisk together the 1 cup of granulated sugar, ½ cup of flour, cinnamon, nutmeg, and kosher salt.

Pour this dry spice mixture directly over the sliced peaches. Toss gently until the fruit is evenly coated. Allow the mixture to sit for 5 minutes so the sugars osmotically draw out the fruit juices.

Pour the entire peach mixture into a large colander set over a bowl. Drain the excess liquid. (This crucial architectural step removes heavy water weight, preventing a soggy bottom crust).

On a well-floured board, roll one dough disk from the center outward into a circle 1 inch larger than your 9-inch pie pan. Gently ease the dough into the pan without stretching it.

Brush the bottom of the raw crust with a light layer of the egg wash, and pierce the bottom several times with a fork to allow steam to escape.

Pour the drained, spiced peaches directly into the crust. Dot the top of the fruit evenly with the tiny cubes of cold butter.

Roll the second dough disk out and place it gently over the top of the pie. Fold the overhanging edges under and crimp firmly with your fingers to seal the pie.

Use a paring knife to cut several small steam vents into the top crust. Brush the entire surface heavily with the remaining egg wash.

Place the pie pan onto a heavy metal baking sheet to catch any bubbling juices. Bake at 400°F until the crust is deeply golden brown and the fruit filling is thick and bubbling vigorously through the vents, about 45 to 50 minutes. Allow to cool and set before slicing.