Crust Ingredients: 1/2 (14.1-oz.) package refrigerated piecrusts Parchment paper 1 egg yolk, lightly beaten 1 tablespoon whipping cream Filling Ingredients: 1/4 cup butter, melted 1 cup sugar 1/4 teaspoon salt 3 large eggs 3 cups lightly packed, cooked, mashed sweet potatoes (about 2 1/2 lb. sweet potatoes) 1 cup half-and-half 1 tablespoon lemon zest 3 tablespoons lemon juice 1/4 teaspoon ground nutmeg Marshmallow Meringue Ingredients: 3 egg whites 1/2 teaspoon vanilla extract 1/8 teaspoon salt 1/4 cup sugar 1 (7-oz.) jar marshmallow crème Instructions: Prepare crust: Preheat oven to 425°. Roll piecrust into a 13-inch circle on a lightly floured surface. Fit into a 9-inch pie plate; fold edges under, and crimp. Prick bottom and sides with a fork. Line piecrust with parchment paper; fill with pie weights or dried beans. Bake 9 minutes. Remove weights and parchment paper. Whisk together egg yolk and cream; brush botto...