Pulse together all-purpose flour, granulated sugar, and salt in a food processor until combined. In a bowl, whisk an egg with white vinegar and ice water, then mix this into the dry ingredients. Add cold, cubed unsalted butter and pulse until a crumbly texture forms. Chill the dough for 30 minutes in the refrigerator.

Lightly flour your work surface and roll the dough into a 12-inch circle. Transfer it to a 9-inch pie plate, gently pressing it into the edges and trimming any excess. Crimp the edges decoratively, then bake the crust at 375°F for 15 minutes until lightly golden. Allow it to cool.

In a mixing bowl, whisk together eggs, pure canned pumpkin, sour cream, bourbon, and vanilla extract until smooth. Stir in the ground spices. Simmer the pure maple syrup in a saucepan, then whisk it into the heavy cream before combining it with the pumpkin mix.

Pour the pumpkin filling into the pre-baked crust, smoothing it with a spatula. Bake at 350°F for 55–60 minutes until it sets but still jiggles slightly in the center. Cool completely before refrigerating overnight.

Before serving, sprinkle an even layer of granulated sugar over the pie. Caramelize with a kitchen torch until it bubbles and turns golden brown, or under a broiler for 2-3 minutes, watching closely.