Preheat your oven to 375°F. Grease a deep 9x13 inch baking dish.
In a large skillet, brown the beef and sausage together until fully cooked. Drain the grease.
Stir in the marinara sauce and Italian seasoning. Let it simmer on low for 15 minutes.
Meanwhile, boil lasagna noodles in salted water until just under al dente. Drain and set aside.
In a medium bowl, beat together the softened cream cheese, ricotta, sour cream, and egg until smooth.
To assemble, spread 1 cup of meat sauce in the bottom of the dish.
Top with a layer of noodles, half of the white cheese mixture, 1.5 cups of meat sauce, and 1 cup of mozzarella.
Repeat the layers (noodles, white cheese, meat sauce, mozzarella).
Finish with a final layer of noodles, the remaining meat sauce, and the remaining mozzarella and Parmesan.
Cover with foil and bake for 25 minutes. Remove foil and bake for another 20–25 minutes until golden and bubbling.
Let rest for 20 minutes before slicing.