01 - In a bowl, combine ricotta cheese, egg, salt, and pepper until thoroughly blended.
02 - In a large bowl, toss the cooked ziti with half of the marinara sauce until coated.
03 - Spread half of the pasta mixture into a baking dish. Top evenly with ricotta mixture, half of the mozzarella, and remaining pasta. Pour over the remaining marinara sauce and sprinkle with the remaining mozzarella.
04 - Sprinkle grated Parmesan cheese over the top. Cover the dish with aluminum foil.
05 - Place the assembled dish in the freezer until ready to bake.
06 - When ready to serve, bake the covered frozen casserole at 375°F (190°C) for 50–60 minutes, or until hot and bubbling throughout.