For the Chocolate Pie Dough: Pulse cocoa powder, granulated sugar, salt, and 1 ¼ cups plus 1 Tbsp flour in a food processor to combine. Add butter and shortening and pulse until mixture resembles coarse meal with a few pea-sized pieces of butter remaining. Transfer to a large bowl.
Whisk together egg yolk, vinegar, and ¼ cup ice water in a small bowl. Drizzle half of egg mixture over flour mixture and, using a fork, mix gently just until combined. Add remaining egg mixture and mix until dough just comes together (you will have some unincorporated pieces).
Turn out dough onto a lightly floured surface, flatten slightly, and cut into quarters. Stack pieces on top of one another. Placing unincorporated dry pieces of dough between layers, and press down to combine. Repeat process twice more (all pieces of dough should be incorporated at this point). Form dough into a 1” thick disk. Wrap in plastic; chill at least 1 hour.
Roll out disk of dough on a lightly floured surface into a 14” round. Transfer to a 9” pie dish. Lift up edge and allow dough to slump down into dish. Trim. Leaving about 1” overhang. Fold overhang under and crimp edge. Chill in freezer 15 minutes.
When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 to 5 minutes). Set the temperature to 350 and preheat, lid closed, for 10 to 15 minutes.
Line pie with parchment paper or heavy-duty foil, leaving a 1 ½” overhang. Fill with pie weights or dried beans. Bake until crust is dry around the edge, about 20 minutes. Remove paper and weights and bake until surface of crust looks dry, 5-10 minutes. Brush bottom and sides of crust with 1 beaten egg. Return to grill and bake until dry and set, about 3 minutes longer.
For the Pumpkin Maple Filling: Whisk together pumpkin puree, sour cream, bourbon, cinnamon, salt, ginger, nutmeg, allspice and remaining 3 eggs in a large bowl; set aside.
Pour maple syrup and 2 tbsp sugar in a small saucepan. Scrape in the seeds from vanilla bean (reserve pod for another use) or add vanilla extract and bring syrup to a boil. Reduce heat to medium-high and simmer, stirring occasionally, until mixture is thickened and small puffs of steam start to release, about 3 minutes.
Remove from heat and add cream in 3 additions, stirring with a wooden spoon after each addition until smooth. Gradually whisk hot maple cream into pumpkin mixture.
Place pie dish on a rimmed baking sheet and pour in pumpkin filling. Bake pie, rotating halfway through, until set around edge but center barely jiggles, 50-60 minutes.
Transfer pie dish to a wire rack and let pie cool. Slice and serve. Enjoy!
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