Preheat oven to 425 degrees. If using fresh pumpkin, roast it, 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.) Reduce oven temperature to 375 degrees.
Reserve 1 disk of dough for making leaf decorations. On a lightly floured work surface, roll out remaining disks into 14-inch rounds. Fit rounds into two 10-inch pie plates; trim edges, leaving 1/2-inch overhangs. Fold edges under, and press to seal. Freeze until firm, about 15 minutes.
Roll out reserved disk to a 1/8-inch thickness. Transfer to a baking sheet, and freeze until firm, about 15 minutes. Using a small (about 1 inch) leaf-shape cookie cutter or a paring knife, cut leaves from dough. Freeze until cold, about 15 minutes.
Brush edges of pie shells with a damp pastry brush; arrange leaves around edges, pressing to adhere. Whisk 1 egg and cream in a small bowl. Brush leaves with egg wash. Cut 2 large circles of parchment; fit into pie shells, extending above edges. Fill with pie weights or dried beans.
Bake pie shells 15 minutes. Remove weights and parchment; bake until golden brown, 15 to 20 minutes more. Cool completely on wire racks.
If using fresh pumpkin, discard seeds. Scoop out flesh, using a large spoon, into a food processor. Process until smooth, about 1 minute. Measure out 3 cups, and transfer pumpkin to a large bowl (reserve any remaining for another use; if using canned pumpkin, add that to the bowl instead). 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 pie shells on rimmed baking sheets. Divide pumpkin mixture evenly between shells. Bake until all but centers are set, 35 to 40 minutes. Let pies cool completely on wire racks. Cut into wedges, and serve with whipped cream.
To prepare the pies in stages, make the dough and either freeze or refrigerate, then roll out, fit into pie plates, and chill again. The shells can be covered tightly and refrigerated for a day or two or frozen for longer (thaw in refrigerator before proceeding).