In a saucepan, melt butter over medium heat. Saute onion and garlic until tender. Stir in flour and salt; cook until bubbly. Gradually stir in broth and milk, bring to a boil, stirring constantly. Boil for one minute. Stir in 2 cups mozzarella, 1/2 cup Parmesan cheese, basil, oregano and pepper; set aside.
In a bowl, combine the ricotta cheese, parsley and remaining mozzarella; set aside.
Spread 1/4 of the cheese sauce into a greased 13x9 baking dish; cover with 1/3 of the noodles. Top with half of the ricotta mixture, half of the spinach and half of the chicken. Cover with 1/4 of cheese sauce and 1/3 of the noodles. Repeat layers of ricotta mixture, spinach, chicken and 1/4 cheese sauce. Cover with remaining noodles and cheese sauce.
Sprinkle with remaining Parmesan cheese. Bake, uncovered, at 350 for 35-40. Let stand 15 minutes before cutting.