Whisk together the mayo, sour cream, olive oil, vinegar, Parmesan until well mixed. Add in dry Italian Dressing mix stir until well blended. Season with salt and pepper, to taste. Makes about 3/4 cup.
Notes
Feel free to add more milk 1 tablespoon at a time until you reach your desired consistency.
You can substitute the herbs for whatever you like. Basil or tarragon would be yummy!