Preheat your oven to 350°F (175°C). This ensures your casserole bakes evenly and comes out perfectly cooked.
In a large skillet, cook 1 lb of ground beef over medium heat along with 1 small chopped onion and 2 cloves of minced garlic. Sauté until the ground beef is browned and the onion is translucent, around 5-7 minutes. Make sure to drain any excess fat from the skillet.
Add 1 jar (24 oz) of marinara sauce and 1 can (15 oz) of crushed tomatoes to the skillet. Stir to combine and season with salt and pepper to taste, as well as 1 tbsp of Italian seasoning. Let the sauce simmer for about 10 minutes to meld the flavors together.
In a large baking dish, start layering your ingredients. Begin with a layer of the meat sauce at the bottom. Follow this with a layer of 1 package (25 oz) frozen cheese ravioli.
Next, spoon in 1 cup of ricotta cheese, followed by 1/2 cup of sour cream and 1 package (8 oz) of softened cream cheese, dolloping it over the ravioli. Then sprinkle 2 cups of shredded mozzarella cheese on top.
Repeat the layering process by adding more meat sauce, another layer of ravioli, ricotta, sour cream, cream cheese, and finishing with the remaining mozzarella cheese.
Once your layers are complete, top the casserole with 1/2 cup of grated Parmesan cheese for an extra cheese kick.
Cover the baking dish with aluminum foil and bake for 30 minutes. Remove the foil and continue baking for another 10-15 minutes, until the cheese is bubbly and golden brown.
Allow the casserole to cool slightly before garnishing with fresh chopped parsley (if desired). Serve warm, and enjoy your delicious creation!