Garlic Herb Ranch Dressing

This is a copy-cat recipe for the dressing at California Pizza Kitchen. Katie found it and we love it on our Cafe Rio Salads. I've learned from experience that you CAN NOT use Miracle Whip in place of the Mayo. It turns out disgusting. This is a good all around dressing that you could use on anything!
And we always half the recipe, it makes a ton! Here is the full recipe:

Garlic Herb Ranch Dressing
1/2 teaspoon dry mustard
1/4 teaspoon cold water
2 3/4 cups mayonnaise (neither Katie or I ever put that much in..I would only put 2 at the most)
1 cup buttermilk
7 tablespoons sour cream
2 1/2 tablespoons apple cider vinegar
1-1/2 teaspoons thinly sliced scallions (green and whites)
2 teaspoons minced garlic
2 teaspoons minced fresh Italian parsley
1-1/2 teaspoons Worcestershire sauce
1 teaspoon minced fresh dill
1/2 teaspoon minced fresh oregano (or 1/4 teaspoon dried)
1/2 teaspoon freshly ground black pepper
1/4 teaspoon minced fresh basil

In a mixing bowl, use a fork to stir together the mustard and cold water, forming a paste. Set aside for 10 minutes. Add the remaining dressing ingredients to the bowl and, using a handheld mixer at low speed or a whisk, blend together just until smooth, taking care not to incorporate too much air into the dressing. Cover with plastic wrap and refrigerate.