We tossed this tangy dressing with chilled romaine lettuce and thinly sliced red onions for a simple yet satisfying side.
In a medium bowl, whisk together mayonnaise, sour cream, buttermilk, garlic, salt, honey, and vinegar until smooth. Fold in basil and blue cheese. Season with pepper and more salt, as desired. Cover with plastic wrap; store in the refrigerator until ready to use, up to 3 days.
This is best made at least several hours ahead of time to let the flavors blend. Keep it in the refrigerator, covered, until ready to serve.