Preheat your oven to 375°F (190°C).

Cook manicotti shells in a large pot of boiling salted water for 6-7 minutes, until just al dente. Drain and lay on a baking sheet to cool slightly.

Brown the ground beef and Italian sausage in a large skillet over medium heat. Add chopped onion and cook for about 8 minutes until the meat is browned and onions are translucent. Drain excess fat.

Add minced garlic to the skillet and sauté for about 1 minute until fragrant. Pour in the marinara sauce and let it simmer for 10 minutes.

Combine filling ingredients by mixing ricotta cheese, reserved mozzarella, parmesan, egg, dried basil, oregano, salt, and pepper in a bowl until creamy.

Spread half of the meat sauce in the bottom of a baking dish. Fill each manicotti shell with the ricotta mixture and arrange them seam-side down in the dish.

Cover the stuffed shells with the remaining meat sauce and sprinkle reserved mozzarella on top.

Cover the dish with foil and bake for 30 minutes. Then uncover and bake for an additional 10 minutes.

Let the manicotti rest for 5 minutes before serving.

Optional: Garnish with fresh basil before serving.