Ready to dive into the cooking process? Let’s break it down into easy-to-follow steps:

1. Preheat Your Oven: Start by preheating your oven to 375°F (190°C). This ensures your casserole cooks evenly and gets that delightful golden-brown topping.
2. Cook the Ravioli: Bring a large pot of salted water to a boil. Add the frozen ravioli and cook according to the package instructions (usually about 5-7 minutes) until they are al dente. Be careful not to overcook them since they will bake further in the casserole. Drain and set aside.
3. Mix the Cheeses: In a medium bowl, combine the ricotta cheese, half of the shredded mozzarella, and half of the grated Parmesan cheese. Add the Italian seasoning, and season with salt and pepper to taste. This creamy mixture will add a rich layer to your casserole.
4. Layer the Casserole: In a 9×13-inch baking dish, spread a thin layer of marinara sauce on the bottom. Then, add half of the cooked ravioli on top, followed by half of the ricotta cheese mixture. Spread it gently to cover the ravioli. Pour half of the remaining marinara sauce over the cheese mixture, and sprinkle with more mozzarella and Parmesan. Repeat the layering process with the remaining ingredients—ravioli, ricotta mixture, marinara sauce, and finally, top it all with the remaining mozzarella and Parmesan cheese.
5. Bake the Casserole: Cover the baking dish with aluminum foil (this helps retain moisture). Bake in the preheated oven for 20 minutes. After that, remove the foil and bake for an additional 15-20 minutes, or until the cheese is bubbly and golden brown.
6. Let it Rest: Once baked, remove the casserole from the oven and let it rest for about 10 minutes. This helps the layers set and makes it easier to serve.
7. Serve and Enjoy: Slice into squares and serve with a sprinkle of fresh basil or parsley for a pop of color. Pair it with a side salad or garlic bread for a complete meal!