1. Prepare Oven and Dish:

• Preheat your oven to 375°F (190°C).
• Grease a 9×13-inch baking dish with nonstick spray or a little olive oil.

2. Prepare the Meat Sauce:

• In a large skillet over medium-high heat, cook the ground beef (or Italian sausage) and chopped onion until the meat is fully browned and the onion has softened, approximately 5-7 minutes. Break the meat apart as it cooks.
• Drain off any excess fat from the skillet.
• Add the minced garlic to the skillet and cook for about 1 minute more, until fragrant.
• Stir in the jar of marinara sauce. Bring the mixture to a simmer and let it cook gently for 5 minutes for the flavors to meld. Remove from heat and set aside.

3. Make the Ricotta Mixture:

• While the meat sauce simmers, prepare the ricotta filling. In a medium bowl, combine the ricotta cheese, sour cream, softened cream cheese, egg, chopped fresh parsley (or dried), salt, and pepper.
• Mix with a spoon or spatula until the mixture is smooth, creamy, and well combined.

4. Assemble the Casserole Layers:

• Layer 1: Spread a thin layer (about 1/2 to 1 cup) of the meat sauce evenly over the bottom of the prepared baking dish.
• Layer 2: Arrange half of the uncooked frozen or fresh ravioli in a single layer over the sauce.
• Layer 3: Spread half of the ricotta mixture evenly over the ravioli layer.
• Layer 4: Top the ricotta mixture with half of the remaining meat sauce.
• Layer 5: Sprinkle with 1 cup of the shredded mozzarella cheese.
• Layer 6: Arrange the remaining uncooked ravioli in a single layer.
• Layer 7: Spread the remaining ricotta mixture evenly over the second ravioli layer.
• Layer 8: Top with the rest of the meat sauce, spreading it to cover the ricotta mixture.
• Layer 9: Sprinkle evenly with the remaining 1 cup of mozzarella cheese and the 1/2 cup of grated Parmesan cheese.

5. Bake Covered:

• Cover the casserole dish tightly with aluminum foil. This traps steam to cook the ravioli.
• Place the covered dish in the preheated oven and bake for 30 minutes.

6. Bake Uncovered:

• Carefully remove the aluminum foil from the baking dish (watch for steam).
• Return the dish to the oven and bake uncovered for an additional 10-15 minutes.
• The casserole is done when the cheese topping is melted, bubbly, and lightly golden brown around the edges, and the filling is hot.

7. Rest and Serve:

• Let the casserole cool for 5-10 minutes before slicing and serving. This allows the layers to set slightly, making it easier to serve neat portions.
• Garnish with extra chopped fresh parsley, if desired. Serve hot.