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 with butter or cooking spray.
03 - Heat olive oil in a large skillet over medium heat. Add chopped onion and cook until soft, about 5 minutes. Add minced garlic and cook for 1 minute more until fragrant.
04 - Add chopped silverbeet to the skillet and cook until wilted and any liquid has evaporated, about 5–7 minutes. Remove from heat and let cool slightly.
05 - In a large bowl, combine ricotta, grated parmesan, 4 eggs, nutmeg, salt, and black pepper. Mix until well blended, then stir in the cooled silverbeet mixture.
06 - Roll out chilled pastry on a lightly floured surface to fit the pie dish. Carefully transfer dough to the dish, pressing it into the bottom and up the sides. Trim any excess dough from the edges.
07 - Spoon the filling evenly into the pastry shell. Beat the remaining egg and brush the pastry edges with egg wash. Pour any remaining egg over the filling.
08 - Sprinkle the top with 2 tablespoons grated parmesan. Bake for 40–45 minutes until filling is set and pastry is golden brown. Let cool for 10–15 minutes before slicing.