- Using the pumpkin ice cream starter, half-and-half and cream, prepare the ice cream according to the package instructions. Place the ice cream in the freezer.
- Position a rack in the lower third of an oven and preheat to 375°F. In a small bowl, stir together the egg yolks, the 2 tablespoons water and the vanilla; set aside.
- In a food processor, pulse together the flour, sugar and salt until combined. Add the butter and pulse until the texture resembles coarse cornmeal. Add the egg yolk mixture and pulse until the dough just comes together. The dough should hold together when squeezed with your fingers but should not be sticky. If it is crumbly, add more water 1 tablespoon at a time, pulsing a few times after each addition.
- Transfer the dough to a work surface and divide into 2 balls. Flatten 1 ball into a disk, wrap with plastic wrap and refrigerate until well chilled, about 1 hour. Press the other ball of dough firmly and evenly into the bottom of a 9-inch springform pan. Line the pan with parchment paper and fill with pie weights. Bake the crust for 15 minutes, then carefully remove the parchment and weights and continue baking until the crust is golden, 16 to 18 minutes more. Transfer the pan to a wire rack and let cool completely.
- On a lightly floured work surface, roll out the chilled dough disk about 3/16 inch thick and make decorative cutouts according to the package instructions for the fall piecrust cutters. Transfer the cutouts to a parchment-lined baking sheet and brush with the egg mixture. Bake until golden, 15 to 17 minutes, rotating the pan halfway through baking. Transfer to a wire rack and let the cutouts cool completely.
- When the crust is completely cool, remove the ice cream from the freezer and let stand at room temperature until softened, 15 to 20 minutes. Transfer the ice cream to the crust and spread evenly. Cover with plastic wrap and freeze until the ice cream is firm, at least 4 hours or up to overnight.
- Remove the plastic wrap from the ice cream pie and let stand at room temperature for 5 minutes. Remove the outer ring from the springform pan.
- To make the whipped cream, in the bowl of an electric mixer fitted with the whisk attachment, beat together the cream, nutmeg, sugar, cinnamon and vanilla on medium-high speed until soft peaks form, about 2 minutes. Top the pie evenly with the whipped cream and decorate as desired with the baked cutouts.