Preheat oven to 425 degrees. If using fresh pumpkin, roast pumpkin, cut sides down, on a rimmed baking sheet until soft, 50 to 60 minutes. Let cool completely. Roasted pumpkin can be refrigerated in an airtight container overnight.
Reserve 1/4 of the dough for making leaf decorations. Turn out the remaining dough onto a lightly floured work surface; divide in half. Roll out each half into a 14-inch round. Fit rounds into two 10-inch pie plates; crimp edges as desired. Freeze until firm, about 15 minutes.
Roll out reserved dough to 1/8 inch thick. Transfer to a baking sheet, and freeze until firm, about 15 minutes. Using a leaf-shape cookie cutter or a paring knife, cut leaves from dough. Freeze until cold, about 10 minutes.
Reduce the oven temperature to 375 degrees. Whisk 1 egg and heavy cream in a small bowl; set aside. Brush edges of pie shells with a wet pastry brush; arrange leaves around edges, pressing to adhere. Brush leaves with egg wash. Cut 2 large circles of parchment; fit into pie shells, extending above edges. Fill with pie weights. Freeze until cold, about 10 minutes.
Bake pie shells 10 minutes. Remove weights and parchment; bake 5 minutes more. Let cool completely on a wire rack.
If using fresh pumpkin, discard seeds. Scoop out flesh using a large spoon; transfer to a food processor. Process until smooth, about 1 minute. Transfer pumpkin to a large bowl. Add brown sugar, cornstarch, salt, cinnamon, ginger, vanilla, nutmeg, remaining 6 eggs, and evaporated milk; whisk until combined.
Reduce oven temperature to 350 degrees. Place pies on a rimmed baking sheet. Divide pumpkin mixture evenly between shells. Bake until all but centers are set, 35 to 40 minutes. Let pies cool completely on a wire rack. Cut into wedges, and serve with whipped cream.