01 - Combine flour and salt in a large bowl. Rub in cold butter until mixture resembles coarse crumbs. Add cold water one tablespoon at a time, mixing until dough just comes together. Shape into a disc, wrap in plastic, and refrigerate for 30 minutes.
02 - Preheat oven to 350°F. Grease a 9-inch pie dish.
03 - Heat olive oil in a large skillet over medium heat. Add onion and cook until soft, about 5 minutes. Add garlic and cook for 1 minute more.
04 - Add chopped silverbeet and cook until wilted and any liquid has evaporated, about 5–7 minutes. Remove from heat and cool slightly.
05 - In a large bowl, combine ricotta, grated parmesan, 4 eggs, nutmeg, salt, and black pepper. Stir in the cooled silverbeet mixture.
06 - Roll out the chilled pastry on a lightly floured surface and line the pie dish. Trim excess dough.
07 - Spoon the filling evenly into the pastry shell. Beat the remaining egg and brush the pastry edges with it; pour the rest over the filling.
08 - Sprinkle the top with the extra 2 tablespoons grated parmesan.
09 - Bake for 40–45 minutes or until the filling is set and the pastry is golden. Cool slightly before slicing.