Preheat your oven to 350°F (175°C).

In a large skillet, combine the ground beef and Italian sausage over medium heat, cooking until fully browned, about 8-10 minutes. Drain any excess fat.

Add the chopped onion and minced garlic to the skillet, sauté for approximately 5 minutes until soft and translucent.

Stir in crushed tomatoes, tomato paste, oregano, basil, salt, and pepper. Simmer the sauce uncovered for 15 minutes over low heat, stirring occasionally.

Bring a large pot of salted water to a boil. Add manicotti shells and cook for 6-8 minutes until al dente. Drain and rinse under cold water.

In a mixing bowl, combine ricotta cheese, half of the mozzarella, half of the parmesan, and the egg. Season with salt and pepper.

Fill each manicotti shell with the cheese mixture using a piping bag or spoon.

Spread a thin layer of meat sauce in a baking dish, arrange the stuffed manicotti shells, and pour remaining sauce over the top.

Sprinkle remaining mozzarella and parmesan cheese over the stuffed shells.

Cover with foil and bake for 25 minutes. Remove foil and bake for an additional 15 minutes until bubbly and golden.

Let cool for a few minutes before serving, garnished with fresh parsley.