Preheat your oven to 350°F (175°C) and lightly coat a 2-quart casserole dish with non-stick spray.
In a large mixing bowl, combine cream of chicken soup, sour cream, and Italian seasoning until smooth.
Add shredded or diced chicken, folding it into the sauce until well-coated.
Transfer the chicken mixture to the prepared casserole dish, spreading it evenly.
Crush the Ritz crackers and sprinkle them over the chicken mixture. Drizzle melted butter over the crackers.
Bake uncovered for 25 to 30 minutes, or until the cracker topping is golden and the filling is bubbling.
Remove from oven and let it cool for a few minutes before serving.
