Sprinkle the garlic with a pinch of salt and mash to a paste. In a bowl, whisk together the garlic, sour cream, mayonnaise and vinegar. Whisk in the buttermilk and season with pepper.
NOTES Blue Cheese Dressing Add 2 ounces crumbled blue cheese. Tzatziki Dressing Add 2 ounces crumbled feta cheese and 1 tablespoon chopped dill