01 - In a mixing bowl, whisk together flour, salt, and sugar. Incorporate cold butter using a pastry cutter or fork until the mixture forms coarse crumbs. Gradually add ice water, 1 tablespoon at a time, mixing until dough forms. Shape into a disk, wrap with plastic, and chill for at least 1 hour.
02 - Set oven temperature to 375°F (190°C).
03 - On a lightly floured surface, roll out the dough to fit a 9-inch pie pan. Transfer and gently press into the pan, trimming excess and crimping edges. Chill pan for 15 minutes.
04 - Line unbaked pastry with parchment paper, fill with pie weights or dried beans. Bake for 15 minutes. Remove weights and parchment, bake an additional 8 to 10 minutes until lightly golden. Allow to cool slightly.
05 - Melt brown sugar and butter in a saucepan over medium heat, stirring continuously until mixture is bubbly and thickened, about 2 to 3 minutes. Remove from heat.
06 - In a large bowl, whisk together cornstarch, cinnamon, ginger, nutmeg, salt, and eggs. Add milk and heavy cream gradually while whisking. Incorporate pumpkin purée and vanilla extract. Whisk in the warm butterscotch mixture slowly to avoid curdling.
07 - Pour prepared filling into prebaked crust. Bake for 35 to 40 minutes, until edges are set and center remains slightly jiggly. Let cool to room temperature, then refrigerate for at least 2 hours to allow setting.
08 - With an electric mixer, beat heavy whipping cream, powdered sugar, and vanilla until soft peaks form. Spread or pipe over chilled dessert.
09 - Cut into portions and serve chilled.