Prepare and roll out the pie crust. Transfer it to a standard 9-inch pie dish. Trim the edges and fold them under themselves before crimping with your fingers or a fork. Cover the crust with plastic wrap and refrigerate it for at least 30 minutes or up to 1 day.
Place a rack in the center of the oven and preheat to 375 degrees F.
To prepare the filling, scrub and peel the sweet potatoes. Then, dice into large, 3-inch chunks. Place chunks in a large pot and cover with cool water. Bring the pot to a boil, then reduce the heat to medium. Let simmer until the potatoes are tender and pierce easily with a thin knife, about 15 to 20 minutes.
Drain the potatoes into a colander, transfer back into the pot, and mash. Measure out 2 cups, which is the amount that you need for the pie, and reserve any extra for another recipe.
To the same pot, add the brown sugar, cinnamon, ginger, allspice, salt, butter, and 5 ounces (1/2 cup plus 2 tablespoons) of evaporated milk. Place the pot on the stove and cook on low for about 5 minutes, mashing the potatoes further as they cook.
To make the silkiest possible pie, use an immersion blender to puree until totally smooth; you may also transfer the mixture to a blender or food processor. Once the mixture is smooth and smells very fragrant, remove from the heat and let cool in the pot.
While the sweet potato mixture cools, whisk together the remaining 1/2 cup plus 2 tablespoons (5 ounces) of evaporated milk, granulated sugar, eggs, bourbon, and vanilla extract, in a separate bowl until totally smooth.
Carefully pour the egg mixture into the warm sweet potato mixture and stir until evenly and smoothly combined.
Remove the crust from the refrigerator, pour the prepared filling into the pie crust, and then gently place the pie dish on a baking sheet. Bake the pie for 10 minutes at 375 degrees F, then reduce the heat to 325 degrees F and continue baking until cooked through; about 50 minutes. Check the pie periodically. If the crust is browning more quickly than you would like, shield it, then continue baking as directed. When the pie is ready, remove, and let cool completely.*
Finally, prepare the whipped cream. Place the cream in the bowl of a stand mixer fitted with the paddle attachment.** Begin beating on low, then slowly increase the speed to high, beating just until soft peaks form. Add the vanilla. Beat on high, scraping down the sides of the mixer a few times, until a loose whipped cream forms. The cream should be harder than soft peaks but not as stiff as hard peaks. Serve the pie at room temperature, with whipped cream.
*TIP: To test a sweet potato pie for doneness, lightly wiggle the baking sheet. If the center of the pie has a pronounced, wavy jiggle, it needs additional time in the oven. If the center of the pie has a lighter, more structured jiggle, it’s done. Remove from the oven, place the pie dish on a wire rack, and let cool.
**TIP: When whipping cream, put your mixing bowl and beaters in your freezer or refrigerator first; the colder they are, the fluffier the cream.
TO STORE: Gently cover your pie and store it in the refrigerator for up to 5 days. Let come to room temperature prior to serving.
TO FREEZE: Bake your pie as directed in a disposable aluminum pie pan (leaving your pie dish available for other recipes). Tightly wrap your cooked and cooled pie in plastic wrap or aluminum foil, and store in a freezer-safe storage container or ziptop bag for up to 3 months. Let the pie thaw for at least 12 hours in the refrigerator before serving.