Step 1Preheat oven to 375˚F. Cook pasta in a large pot of salted water until al dente according to package instructions then drain hot water and add cold water to the pot to stop the cooking process and prevent noodles from sticking together. Shred 4 cups of chicken.Place a pot or large saucepan over medium heat, add 1 Tbsp olive oil and saute onions for 3-4 minutes or until softened. Add 4 Tbsp butter and whisk in 1/3 cup flour. Continue whisking 3 minutes or until flour mixture is golden.Add 2 1/2 cups chicken broth, 1 1/2 cups half and half, 2 tsp salt, and 1/2 tsp black pepper. Whisk until smooth and simmer 5 minutes until thickened to a light gravy consistency.Add minced garlic and chopped spinach, and stir to combine then remove from heat.In a large bowl, whisk together: ricotta, egg, 2 cups mozzarella cheese, 1/4 cup parmesan, and 1/4 cup parsley.Add a little bechamel sauce on the bottom of a 9x13 casserole dish, add 3 noodles, Add 1/2 ricotta sauce, 1/2 shredded chicken then ladle 1/3 of spinach sauce over the chicken.Add 3 noodles, 1/2 ricotta cheese, 1/2 shredded chicken, and 1/3 spinach sauceAdd 3 noodles, remaining 1/3 sauce, and sprinkle on reserved 1 cup cheese.Cover and Bake: Arrange 10-12 toothpicks over the top to keep the foil from touching the cheese then cover with a large sheet of foil. Bake on the center rack in a preheated oven at 375˚F for 45 minutes then uncover and broil 2-3 minutes to brown the cheese. Rest at least 10 minutes uncovered before slicing.