Preheat the Oven:
Preheat your oven to 375°F (190°C). Grease a 9×13-inch baking dish with nonstick spray or a little olive oil.
Prepare the Meat Sauce:
In a large skillet over medium heat, cook the ground beef and onion until the meat is browned and the onion is softened, about 5-7 minutes. Drain any excess fat.
Add the minced garlic and cook for 1 minute, until fragrant.
Stir in the marinara sauce and simmer for 5 minutes. Remove from heat and set aside.
Make the Ricotta Mixture:
In a medium bowl, combine the ricotta cheese, sour cream, cream cheese, egg, parsley, salt, and pepper. Mix until smooth and creamy.
Assemble the Casserole:
Spread a thin layer of the meat sauce on the bottom of the prepared baking dish.
Arrange half of the ravioli in a single layer over the sauce.
Spread half of the ricotta mixture over the ravioli, followed by half of the remaining meat sauce.
Sprinkle with 1 cup of mozzarella cheese.
Repeat the layers with the remaining ravioli, ricotta mixture, meat sauce, and finish with the remaining mozzarella and Parmesan cheeses.
Cover the casserole with aluminum foil and bake in the preheated oven for 30 minutes.
Remove the foil and bake for an additional 10-15 minutes, or until the cheese is melted and bubbly.
Let the casserole cool for 5-10 minutes before serving. Garnish with extra parsley if desired.
