In a food processor, combine all-purpose flour, granulated sugar, and salt, pulsing until mixed. Add cold unsalted butter, blending until the mixture resembles coarse crumbs. In a separate bowl, whisk an egg with white vinegar and ice-cold water. Gradually mix this into the flour mixture until it just comes together. Chill the dough for 30 minutes to firm up.

Once chilled, roll the dough into a 12-inch circle on a lightly floured surface. Carefully fit the dough into a 9-inch pie plate, trimming any excess. Line with parchment paper and fill with pie weights to prevent bubbling. Bake the crust in a preheated oven at 375°F for about 15 minutes, until just set but not browned. Remove from the oven and let cool.

In a large mixing bowl, whisk together the canned pumpkin, sour cream, eggs, bourbon, vanilla extract, and all spices until well combined and smooth. Ensure the mixture is thick but pourable, adjusting the consistency with more sour cream if needed.

Carefully pour the pumpkin filling into the pre-baked crust, smoothing it into an even layer. Gently tap the pie plate on the counter to release any trapped air bubbles. Bake at 350°F for 45 minutes, or until the filling is set but still slightly jiggly in the center.

Once baked, remove the pie from the oven and let it cool completely on a wire rack. After cooling, sprinkle an even layer of granulated sugar over the top. Using a kitchen torch, carefully caramelize the sugar until it forms a crispy, brûléed crust.