Preheat your oven to 375°F (190°C).
Roll out one of the pie crusts and place it in a 9-inch pie dish. Trim any excess dough, leaving about a ½-inch overhang.
Layer the prosciutto slices on the bottom of the pie crust.
In a large bowl, combine the ricotta cheese, eggs, mozzarella cheese, Parmesan cheese, ham, salami, pepperoni, and parsley. Season with salt and pepper to taste. Mix well.
Pour the cheese and meat mixture into the prosciutto-lined pie crust.
Roll out the second pie crust and place it over the filling. Trim the edges and crimp them to seal. Cut a few slits in the top crust to allow steam to escape.
Brush the top of the pie crust with the beaten egg wash.
Bake for 1 hour and 15 minutes, or until the crust is golden brown and the filling is set. If the crust starts to brown too quickly, you can loosely tent it with aluminum foil.
Let the Pizza Rustica cool for at least 20 minutes before slicing and serving.