Instructions:

1. Preheat the Oven: Preheat your oven to 375°F (190°C).

2. Cook the Pasta: In a large pot of boiling salted water, cook the pasta shells according to package instructions until al dente. Drain and set aside to cool slightly.

3. Prepare the Beef Filling: In a skillet over medium heat, add the ground beef, onion, and garlic. Cook until the beef is browned and the onion is translucent, about 5-7 minutes. Drain any excess fat.

4. Mix the Cheese Filling: In a large bowl, combine the ricotta cheese, 1/2 cup of mozzarella cheese, Parmesan cheese, egg, parsley, Italian seasoning, and season with salt and pepper. Stir in the cooked beef mixture until well combined.

5. Stuff the Shells: Using a spoon, carefully fill each cooked pasta shell with the ricotta-beef mixture. Place the stuffed shells in a greased baking dish.

6. Prepare the Sauce: In a separate bowl, mix the marinara sauce with the heavy cream (if using) for extra creaminess. Pour the sauce evenly over the stuffed shells, ensuring they are well covered.

7. Top with Cheese: Sprinkle the remaining 1/2 cup of mozzarella cheese on top of the sauce.

8. Bake: Cover the baking dish with aluminum foil and bake in the preheated oven for 20 minutes. Remove the foil and bake for an additional 10-15 minutes until the cheese is bubbly and golden.

9. Serve: Remove from the oven and let it cool for a few minutes. Garnish with extra parsley before serving. Enjoy this hearty and creamy dish that’s perfect for family dinners!