How to Make It
Prepare the crust: Combine flour, sugar, and salt in the bowl of a food processor and pulse until combined, 3 to 4 times. Add butter and egg; pulse until mixture resembles coarse meal, 8 to 10 times. Sprinkle ice water over dough; pulse until dough begins to form a ball. Turn dough out onto a lightly floured surface; divide in half, and shape into 2 (4-inch) disks. Wrap each in plastic wrap, and refrigerate 30 minutes or overnight.
Preheat oven to 350°F with rack in middle position. Unwrap 1 disk of dough on a lightly floured surface. Roll to a 16-inch circle, and carefully fit into a 9-inch springform pan coated with cooking spray, leaving a 1-inch overhang. Refrigerate until ready to use.
Prepare the filling: Cook Italian sausage in a large nonstick skillet over medium-high, breaking up sausage with a spoon until crumbled and cooked through, 5 to 7 minutes. Transfer sausage to a plate and let cool completely, about 15 minutes. Whisk ricotta, mozzarella, pepper, and 3 of the eggs in a large bowl. Stir in salami, capicola, and ham.
Shingle prosciutto slices in bottom of prepared dough-lined pan. Spread ricotta mixture over prosciutto. Scatter browned sausage over ricotta mixture, pressing lightly into an even layer. Shingle red bell peppers over sausage; top with spinach and Parmesan.
Roll remaining dough into a 12-inch circle on a lightly floured surface. Carefully place over filling. Trim overhang so that it’s even with bottom crust; pinch top and bottom crusts firmly together. Fold dough under and crimp edges.
Lightly beat remaining egg and brush liberally over top of pie. Using a paring knife, cut 4 (1-inch) vents in top of dough in a circular pattern. Place pie on a rimmed baking sheet. Bake until crust is golden brown, about 1 hour. Cover with aluminum foil and bake until a thermometer inserted in center of pie registers 150°F, about 30 more minutes. Transfer pie to a wire rack, and let cool at least 3 hours before serving. Carefully remove sides of pan, and cut pie into slices to serve. Or cool completely, and refrigerate for up to 2 days.