Cook spaghetti according to package directions; drain. Meanwhile, in a large skillet, cook the beef, onion and garlic over medium heat until beef is no longer pink, 6-8 minutes, breaking up beef into crumbles; drain. Stir in the spaghetti sauce, salt and pepper; bring to a boil. Combine meat sauce into the noodles.
In a small bowl, mix egg, cream cheese, sour cream, and parm until blended; stir in green onions. In a greased 9x13-in. baking dish, layer the spaghetti/meat mixture, cream cheese mixture, and top with remaining meat mixture. Cover with shredded cheese.
Bake, covered, at 350° for 25 minutes. Uncover; bake until cheese is bubbly, 5-10 minutes longer.