In a food processor, combine all-purpose flour, granulated sugar, and salt. Pulse until well mixed, then add cold egg, vinegar, and ice water. Cut in cold butter until mixture resembles coarse crumbs. Transfer dough to a bowl, knead gently, wrap in plastic, and chill for 30 minutes.

Preheat oven to 375°F (190°C). Roll chilled dough into a 12-inch circle, fit into a 9-inch pie plate, and trim edges. Line with parchment and fill with pie weights. Bake for 15 minutes, remove weights, brush with egg white, and lower temp to 350°F (175°C).

In a mixing bowl, whisk eggs, canned pumpkin, sour cream, bourbon, and vanilla extract until smooth. Heat maple syrup in a saucepan and slowly stir in heavy cream, mixing into the pumpkin combination.

Pour pumpkin filling into pre-baked crust. Bake at 350°F (175°C) for 55-60 minutes until mostly set but slightly jiggly in the center.

Let pie cool completely at room temperature. Refrigerate overnight. Before serving, sprinkle an even sugar layer and use a kitchen torch to caramelize until deep golden.