Preheat oven to 400F/200C with rack in lowest position.
Line crust with parchment paper, fill with dried beans or pie weights, and bake until crust is set, about 25 minutes; remove beans and parchment and brush bottom and sides of crust with egg white. Bake crust until golden, 10 minutes; let cool completely.
For the filling, whisk together 1 cup maple syrup, brown sugar, and molasses in a saucepan over medium heat. Cook filling, stirring frequently, until sugar dissolves, about 3 minutes; let cool 5 minutes.
Whisk in 4 Tbsp. butter, 2 Tbs bourbon, vanilla, and ¾ tsp salt. Slowly whisk in eggs until incorporated.
Roughly chop 1 cup pecans and add to filling; pour into prepared crust. Toss remaining 1 cup pecans with 1 Tbs maple syrup and 1 Tbs bourbon, then arrange over top of pie. Transfer pie to oven and decrease temperature to 325F/160C
Bake pie until filling is set and center is slightly jiggly, 60–65 minutes. Transfer pie to a rack and let cool completely, 4–5 hours. Serve pie with ice cream.