Preheat oven to 350 degrees. Butter the insides of a 10″ baking dish and set aside.

In a large bowl, mix together the cream of chicken soup and milk until smooth.

Stir in the cooked chicken, green beans, herbs and horseradish mustard together with the soup {making sure to coat the chicken and beans entirely} and spread the mixture into the buttered baking dish.

In a small bowl, combine the crushed Ritz crackers and melted butter until the crushed crackers are coated with the melted butter.

Sprinkle the cracker mixture over the casserole and bake for 30 – 35 minutes. The cracker topping should be a nice golden brown color and the casserole bubbling.

Serve warm.