In a large skillet, heat olive oil over medium heat. Add chopped onion and minced garlic, sauté until fragrant. Add ground beef and Italian sausage, cook until browned. Drain excess fat.

Prepare the Cheese Mixture

In a bowl, combine ricotta cheese, egg, salt, black pepper, and Italian seasoning. Mix well.

Cook the Noodles

Cook the lasagna noodles according to package instructions until al dente. Drain and set aside.

Layer the Lasagna

Spread a thin layer of marinara sauce on the bottom of a 9x13 inch baking dish. Layer 4 noodles over the sauce. Spread half of the ricotta mixture over the noodles, followed by half of the meat mixture, and a third of the mozzarella cheese. Repeat the layers, ending with noodles and marinara sauce. Top with remaining mozzarella and parmesan cheese.

Bake

Cover the dish with aluminum foil and bake in the preheated oven for 25 minutes. Remove the foil and bake for an additional 15 minutes, or until the cheese is bubbly and golden.

Serve

Let the lasagna cool for 10 minutes before slicing and serving.