In a food processor, pulse together the all-purpose flour, granulated sugar, and salt until combined. Add the cold butter and blend until you achieve a coarse texture resembling sand. In a separate bowl, whisk together the egg, vinegar, and ice water, then gradually pour into the flour mixture, mixing until a dough forms. Chill the dough for 30 minutes.

Preheat your oven to 375°F (190°C). Roll out the chilled dough on a floured surface until it's about 1/8 inch thick, then fit it into a pie plate. Place parchment paper over the crust and fill with pie weights or dried beans. Bake for 15 minutes, remove the weights and brush with egg white to seal, then bake for another 5 minutes to set.

In a large mixing bowl, combine the eggs, canned pumpkin, sour cream, bourbon, and vanilla extract, whisking until smooth. In a saucepan, heat the maple syrup and heavy cream over medium heat until just warmed through. Gradually mix the cream mixture into the pumpkin blend, ensuring it's well combined without lumps.

Pour the filling into the prepared crust, smoothing the top. Bake at 350°F (175°C) for 55-60 minutes until set around the edges but slightly jiggly in the center. Let cool completely, preferably overnight in the refrigerator.

Once the pie is cooled, sprinkle granulated sugar over the surface. Using a kitchen torch, carefully caramelize the sugar until it turns golden brown.