Place butter into a large saucepan over medium heat, stirring to melt. Slowly whisk in flour, salt and pepper until smooth and thick, for 1-2 minutes. Slowly whisk in chicken broth until smooth. Increase heat to high whisking until thick, about 2 minutes. Add sour cream, Ranch seasoning, garlic salt, and cooked chicken breast. Stir and season accordingly. You may prefer additional, salt, pepper and garlic salt. I transferred this to my crock pot and kept it on low all day until dinner. You can either serve it immediately or crock pot it until you are ready.
Place rice on serving plates and top with chicken gravy. Have toppings at the table and top with whatever you like! Have fun!