(1) In a wok, heat 2 tablespoons oil over high heat until hot, swirling to coat sides of pan. Add chicken strips and stir-fry until cooked through, but still juicy, 3 to 4 minutes. Remove to a plate.
(2) In same wok, heat remaining 2 tablespoons oil over high heat. Add mushrooms, onion, and garlic. Stir-fry until mushrooms are lightly browned, 3 to 5 minutes. Return chicken to wok.
(3) Pour in marinara sauce. Cook until heated through, about 3 minutes. Add mozzarella and parmesan cheeses. Sprinkle parsley on top. Cover and cook until mozzarella melts, 1 to 2 minutes.
(4) Serve over bed of cooked spaghetti/pasta.