1In a small bowl, mash blue cheese and buttermilk together with a fork until mixture resembles large-curd cottage cheese. Stir in sour cream, mayonnaise, vinegar, sugar, and garlic powder until well blended. Season to taste with salt and pepper.
Whole milk may be used in place of buttermilk for a milder flavor. Dressing may be refrigerated in an air-tight container for up to two weeks.