Preheat oven to 400°F (200°C).

In a large bowl, whisk together flour and salt. Add shortening and butter. Using a pastry cutter or your fingers, cut the fats into the flour until the mixture resembles coarse crumbs.

In a small bowl, beat the egg with a fork. Add to the flour mixture along with ice water and vinegar. Stir gently until the dough comes together and holds when pinched. Add a little more water if needed, 1 teaspoon at a time.

Divide the dough in half. Flatten each half into a disk about ½ inch thick. Place each in a zip-top bag and refrigerate for at least 2 hours or up to overnight.

On a lightly floured surface, roll out one disk into a 13-inch circle. Transfer to a 9-inch deep-dish pie plate. Tuck and crimp edges as desired, then prick the bottom and sides with a fork. Freeze for 30 minutes. Freeze the second disk for future use.

Line the crust with parchment or foil and fill with pie weights or dried beans. Bake for 16–18 minutes, until the edges are lightly golden.

Remove the weights and parchment, prick the crust again, and bake another 7–9 minutes until lightly golden and set. Cool for 10 minutes. Reduce oven temperature to 350°F (175°C).

In a medium saucepan, whisk together cornstarch, salt, and 1 cup sugar. Whisk in the cream until smooth.

Set over medium heat and add 6 Tbsp butter. Bring to a boil, stirring constantly, and boil for 1 minute.

Remove from heat, whisk in vanilla, and pour into the prepared pie crust.

In a small bowl, melt the remaining 2 Tbsp butter. In another bowl, combine cinnamon, nutmeg, and remaining 2 Tbsp sugar. Drizzle melted butter over the filling, then evenly sprinkle the spice mixture on top.

Bake for 25–30 minutes, until fragrant, bubbling, and still slightly jiggly in the center.

Cool pie on a wire rack for at least 2 hours.

Refrigerate for 1 hour before slicing.