Preheat the oven to 350 F. Boil the lasagna noodles until al dente according to package instructions, drain and reserve
Make the bechamel sauce: in a large saucepan over medium heat, melt the butter and sautee the onions and garlic until translucent
Sprinkle the flour on top and cook it for about 2 minutes. Pour in the chicken broth and milk and simmer until the sauce thickens, about 3 minutes. Add 1 ½ cups of shredded mozzarella, ¼ cup parmesan cheese, Italian seasoning, salt and pepper to taste
Mix in the thawed chopped spinach
Assemble the lasagna making the following layers: (use a 9x13-inch baking dish)
⅓ sauce, 3 lasagna noodles, ricotta cheese, dicen chicken, 3 lasagna noodles, ⅓ sauce, 1 ½ cups shredded mozzarella, ½ cup grated parmesan, 3 lasagna noodles, remaining ⅓ sauce, ½ cup shredded mozzarella, ¼ cup parmesan cheese. Bake for 35-40 minutes or until the cheese is melted and slightly browned. Serve with chopped parsley on top