Step 1: Preheat the Oven
Preheat your oven to 375°F (190°C). Grease a 9×13-inch baking dish with nonstick spray or a drizzle of olive oil to keep everything from sticking later.

Step 2: Make the Meat Sauce
Heat olive oil in a large skillet over medium heat. Add the ground beef and chopped onion and cook for 5–7 minutes until the beef is browned and the onion is softened. Drain any excess fat. Stir in the minced garlic and cook for another minute until fragrant. Add the marinara sauce, reduce heat to low, and let it simmer for 5 minutes. Remove from heat and set aside.

Step 3: Mix the Ricotta Layer
In a medium bowl, combine the ricotta cheese, sour cream, softened cream cheese, egg, parsley, salt, and pepper. Mix until smooth. The mixture will be rich, creamy, and easy to spread over the ravioli.

Step 4: Assemble the Casserole
Spoon a thin layer of meat sauce on the bottom of the prepared baking dish to prevent sticking. Arrange half of the ravioli in a single layer. Spread half of the ricotta mixture over the ravioli, followed by half of the remaining meat sauce. Sprinkle with 1 cup of mozzarella. Repeat the layers with the remaining ravioli, ricotta mixture, meat sauce, and then finish with the last cup of mozzarella and all the Parmesan cheese.

Step 5: Bake to Perfection
Cover the dish with aluminum foil and bake for 30 minutes. Then remove the foil and bake uncovered for an additional 10–15 minutes, until the cheese is melted, bubbly, and slightly golden on top.

Step 6: Let It Rest and Serve
Remove from the oven and let the casserole sit for 5–10 minutes before serving. This helps everything set up and makes scooping easier. Garnish with extra parsley if you’d like a pop of color.

Storage Instructions
Leftovers keep beautifully in an airtight container in the fridge for up to 4 days. You can also freeze the baked casserole for up to 2 months. To reheat, bake at 350°F until warmed through or microwave individual portions.