On a lightly floured work surface, roll 1 disk of dough to 1/8 inch thick. Fit into a 9-inch pie plate. Trim edges flush with rim. Refrigerate for 1 hour.
Preheat oven to 375 degrees. Cut a 13-inch round of parchment, and place on top of chilled piecrust. Fill with pie weights or dried beans. Freeze for 10 minutes.
Bake piecrust for 10 minutes. Remove weights and parchment, and continue to bake until barely golden brown, about 5 minutes. Let cool on a wire rack.
On a piece of lightly floured parchment, roll out remaining disk of dough to 1/8 inch thick. Transfer parchment with dough to an inverted baking sheet (this will make it easier to slide it onto pie). Top with an inverted 9-inch pie plate or a cake ring, and gently press to make a light indentation (this will be your guide for cutting the leaf lattice to fit the pie).
Using a 2-inch leaf cutter, cut a pattern out of the round, spacing leaves 1 inch apart and leaving a 1/2-inch border around edge. Transfer leaves to a parchment-lined baking sheet. Using a paring knife or a pizza cutter, cut out the round, leaving an additional 1/2 inch of dough beyond the marked circle. Place in refrigerator while you etch the leaves.
Using a paring knife, etch veins in each leaf. To make egg wash, whisk together egg yolk and 1 tablespoon cream. in a small bowl. Remove leaf lattice from refrigerator, and lightly brush with egg wash. Arrange leaves around edge of lattice, making sure they do not extend over edge or they will brown too quickly. Lightly brush top of each leaf with egg wash as you work to help them adhere. Refrigerate for 20 minutes.
Bake lattice on inverted baking sheet until golden, 20 to 25 minutes. The thin spaces between the leaves will brown before the rest of the crust; tent with foil if crust browns too quickly. Let cool.
Reduce oven to 350. Combine sugar, flour, salt, and spices. In a large bowl, whisk together pumpkin, maple syrup, vanilla, eggs, and remaining 3/4 cup cream. Whisk in flour mixture.
Place partially baked piecrust on a rimmed baking sheet. Pour filling into crust. Bake until slightly puffed and almost set (it should jiggle slightly when shaken gently), 35 to 40 minutes. Remove pie from oven. Using one or two large spatulas, place leaf lattice onto pie. Center it carefully; once lattice has been placed, it cannot be adjusted without smearing the filling. Bake until all but the center of the pie is set, 7 to 10 minutes. Cool completely on a wire rack.