In a large skillet over medium heat, brown the ground beef and Italian sausage. Once cooked, add diced onion and minced garlic, sauté for about 5 minutes.

Stir in crushed tomatoes, tomato paste, sugar, dried basil, salt, and black pepper. Let the sauce simmer on low heat for 30 minutes.

In a medium bowl, combine ricotta cheese, egg, 2 cups of shredded mozzarella, and half of the grated Parmesan cheese. Mix until creamy.

In a large pot of boiling salted water, cook the lasagna noodles according to package instructions, about 8-10 minutes. Drain and rinse under cold water.

Preheat your oven to 375°F (190°C). In a baking dish, spread a layer of meat sauce, followed by noodles, half of the ricotta mixture, a third of the meat sauce, and 1 cup of mozzarella. Repeat layers, finishing with noodles, meat sauce, mozzarella, and Parmesan.

Cover with aluminum foil and bake for 25 minutes. Remove foil and bake for another 25 minutes until golden and bubbly.

Let the lasagna rest for 10-15 minutes. Garnish with parsley if desired, slice, and serve.