In a large skillet, cook the ground beef and Italian sausage over medium heat until browned.

Add the chopped onion and minced garlic to the skillet. Sauté until the onion is translucent, about 5 minutes.

Stir in the crushed tomatoes, tomato paste, oregano, basil, salt, and pepper. Let it simmer for about 30 minutes, stirring occasionally.

While the sauce simmers, cook the lasagna noodles according to package instructions until al dente.

In a mixing bowl, combine the ricotta cheese, egg, Parmesan cheese, and parsley.

Spread a thin layer of meat sauce on the bottom of the baking dish, followed by a layer of noodles, cheese mixture, and mozzarella. Repeat the layers until all ingredients are used.

Cover the baking dish with aluminum foil and bake at 375°F (190°C) for 25 minutes.

Remove the foil and bake for an additional 25 minutes until bubbly and golden brown.

Let the lasagna rest for at least 15 minutes before slicing.