In a large skillet over medium heat, brown the ground beef and Italian sausage for about 5-7 minutes until fully cooked. Drain excess fat and add chopped onion and minced garlic. Cook for another 3-4 minutes until softened, then stir in crushed tomatoes, tomato paste, and season with dried basil and oregano. Let it simmer for 20-30 minutes until thickened.

Meanwhile, bring a large pot of salted water to a boil. Cook the lasagna noodles according to the package instructions, usually about 8-10 minutes until al dente. Drain the noodles and lay them flat on a clean kitchen towel.

In a mixing bowl, combine ricotta cheese, beaten egg, and grated Parmesan cheese. Add chopped parsley and a pinch of nutmeg. Mix until smooth and creamy.

Preheat your oven to 375°F. In a greased baking dish, spread a thin layer of meat sauce first. Place lasagna noodles on top, followed by half of the ricotta mixture and a layer of shredded mozzarella cheese. Repeat the layers and finish with meat sauce topped with mozzarella.

Cover the lasagna with aluminum foil and bake for 35 minutes. Uncover and bake for an additional 10-15 minutes until the cheese is bubbly and golden brown.

Let the lasagna rest for 15 minutes before slicing to allow layers to set.