Pastry: In bowl, whisk together flour, sugar and salt. Using pastry blender or 2 knives, cut in butter until mixture resembles coarse crumbs with a few larger pieces. Drizzle with ice water; toss with fork, adding up to 1 tsp more ice water if needed, to form ragged dough. Shape into disc; wrap in plastic wrap. Refrigerate until chilled, about 1 hour. (Make-ahead: Refrigerate for up to 3 days or freeze for up to 1 month; if frozen, thaw overnight in fridge before continuing with recipe.) Let stand at room temperature for 5 minutes.
On lightly floured work surface, roll out dough into 12-inch circle; fit into 9-inch pie plate. Trim to fit, leaving 1-inch overhang; fold overhang under. Using fork, crimp edge of crust; prick bottom of crust all over. Refrigerate until firm, about 30 minutes.
Line crust with foil; fill with pie weights or dried beans. Bake on rimmed baking sheet on bottom rack of 375°F oven until edge is light golden, 25 to 30 minutes. Remove pie weights and foil; bake on bottom rack until crust is golden, about 10 minutes.
Filling: While crust is baking, in large bowl, beat cream cheese until smooth. Beat in eggs, 1 at a time; beat in pumpkin purée, Demerara sugar, granulated sugar, vanilla, cinnamon, ginger, cloves and nutmeg, scraping down side of bowl, until smooth. (Make-ahead: Cover and refrigerate for up to 4 hours.) Scrape into crust, smoothing top.
Bake on bottom rack of 350°F oven until top is no longer shiny and edge is set yet centre still jiggles slightly, about 35 minutes. Let cool for 45 minutes. Refrigerate until chilled, about 2 hours.
Topping: In bowl, beat together cream, sugar and vanilla until soft peaks form. Spread over filling, leaving 2-inch border. Sprinkle with amaretti crumbs (if using).
Makes 8 to 10 servings.