Preheat oven to 350ºF. Bring a large pot of lightly salted water to a boil. Cook lasagna noodles in boiling water for 8-10 minutes. Drain and rinse with cold water.
Meanwhile, melt the butter in a large saucepan over medium heat. Cook the onion and garlic in the butter until tender, stirring frequently. Stir in flour and salt; simmer until bubbly.
Mix in the broth and milk, and boil, stirring constantly, for 1 minute. Stir in 2 cups of mozzarella cheese and 1/2 cup Parmesan.
Season with basil, oregano and ground black pepper. Remove from heat and set aside.
Spread 1/3 of the sauce mixture on the bottom of the 9×13 inch baking dish. Layer with 1/3 of the noodles, and all of the ricotta and the chicken. Arrange 1/3 of the noodles over the chicken and layer with 1/4 of the sauce mixture, the spinach, and the remaining 2 cups of mozzarella cheese and 1/2 cup Parmesan cheese.
Arrange remaining noodles over cheese and spread remaining sauce evenly over noodles. Sprinkle with parsley and additional 1/4 cup Parmesan cheese (optional).
Bake for 35 to 40 minutes in the preheated oven. Let stand 5 minutes before cutting and serving.