Preheat oven to 350 degrees F. Spray a 9x13-inch baking dish with nonstick cooking spray; set aside.
In a large skillet over medium-high heat, melt butter and sauté onion and garlic for 3-4 minutes, or until onion is tender. Sprinkle flour on top and whisk together until flour begins to turn golden brown.
Mix in chicken broth, milk, salt and pepper and cook, stirring continuously, for 5 minutes or until sauce has thickened. Add spinach and mix until well combined; remove from heat and set aside.
In a mixing bowl, combine ricotta, eggs, 2 cups shredded mozzarella, parmesan cheese, parsley, salt and pepper; set aside.
Spread a thin layer of spinach cream sauce on the bottom of the pan (about 1⁄2 cup), top with 5 lasagna noodles, 1⁄2 the ricotta mixture, 1⁄2 the chicken, 1⁄3 the spinach sauce. Repeat layers. Top with remaining 1⁄3 of the spinach sauce and 1⁄2 cup shredded mozzarella cheese.
Cover with foil and bake for 45 minutes. Remove foil and bake for an additional 15 minutes. Remove from oven and let rest for 5-10 minutes before serving.