Preheat oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish.
- Cook noodles according to package directions if not using oven-ready. Drain and set aside.
- In a saucepan, melt butter over medium heat. Add garlic and cook for 1–2 minutes.
- Whisk in flour and cook for 1 minute. Gradually add milk and broth, whisking constantly to prevent lumps.
- Add Italian seasoning, salt, and pepper. Simmer until thickened, about 4–5 minutes.
- In a bowl, combine shredded chicken with 1/2 cup of the white sauce.
- Spread a thin layer of sauce in the prepared dish. Layer with noodles, half the chicken, dollops of ricotta, some mozzarella, and a drizzle of sauce.
- Repeat layers. Top final layer with noodles, remaining sauce, mozzarella, and Parmesan.
- Cover with foil and bake 25 minutes. Uncover and bake 15 minutes more until golden and bubbly.
- Let rest for 10–15 minutes before serving. Garnish with parsley if desired.