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.