Preheat oven to 350 degrees F. Spray a 9 x 13 casserole dish lightly with cooking spray.
Add chicken to the casserole dish in an even layer.
In a mixing bowl, combine the cream of chicken, green chiles, chicken broth and sour cream.
Pour mixture over chicken.
Top with cheese if desired.
Sprinkle crushed crackers evenly over casserole.
Pour melted butter over the crackers.
Bake, uncovered, for 30 minutes.