In a bowl, stir or whisk together mayonnaise, sour cream, Worcestershire sauce, and lemon juice. Stir in blue cheese (start with 1/2 cup--see note), using the back of a spoon to mash some of the crumbles into the dressing base. Leave some of the crumbles intact for a chunky-style dressing.
Stir in as much buttermilk as needed to create your desired consistency dressing (see note). Stir in chives or parsley. Season to taste with black pepper and add additional Worcestershire sauce and lemon juice, to taste.
Cover and refrigerate for at least an hour for the flavors to meld, preferably longer. The flavor is best after 24 hours.* Store, tightly-covered, in the refrigerator for up to 3-5 days.
*Adjust the buttermilk and quantity of blue cheese based on the texture of dressing you want (dippable vs. pourable), and the pungency of the wedge of cheese you're using. For a very thick dip, you might not need any buttermilk at all! Remember that the dressing will both thicken and intensify in flavor as it stands. Read theFAQ'sabove for additional info about ingredient quantity ranges.For blue cheese recommendations, read "What Kind of Blue Cheese Should I Buy?", in the article above.
For a little garlicky flavor, add garlic powder, to taste, starting with 1/4 teaspoon.
For blue cheese dressing with a kick, add hot sauce, cayenne pepper, or sriracha, to taste.
For a smoky blue cheese dressing, use a smoked blue cheese, such as those available from Cowgirl Creamery or Rogue Creamery.