This salad dressing is also delicious as a topping for baked potatoes.
In a medium bowl, whisk together mayonnaise, sour cream, vinegar, and 1/4 cup cold water. Stir in shallot and blue cheese, breaking up large pieces of cheese with a spoon. Season with salt and pepper.
Try blue cheese dressing over crisp and crunchy greens, such as romaine or iceberg lettuce, or as a topping for baked potatoes.