or yogurt, plain
red wine vinegar
Mix in the egg yolks, mustard, vinegar, and salt together in a bowl.
Drop-by-drop beat in the olive oil until a good, thick maynaise is formed.
Add more oil if needed.
Beat the egg whites until they are stiff but not dry then fold them into the yolk mixture.
Add the sour cream/yogurt to the mixture and stir well.
Cover and refrigerate for 2 to 4 hours.