Combine mayonnaise, sour cream, buttermilk and milk in a bowl and whisk until smooth and well combined. Add the rest of the ingredients and stir well. Chill for at least two hours before using. Thin with more buttermilk or milk if desired.
Recipe by Baked In at https://www.baked-in.com/2012/02/07/buttermilk-ranch-dressing/