In a medium bowl stir together the sour cream, mayonnaise, ¼ of the blue cheese, buttermilk, lemon juice, salt, and pepper. Stir well until smooth. Gently stir in the remaining ¼ cup crumbled blue cheese. Refrigerate for at least 20 minutes before serving. At this point you can store it in the refrigerator up to 3 days.
Remove any limp outer leaves of the iceberg salad and then cut in half, then cut each half into quartered wedges.
Place each wedge on a plate and drizzle with the blue cheese dressing. Top it with a few crumbles of bacon, sprinkle of chives (if using), reserved blue cheese chunks and the tomatoes.
Give one or two more sprinkle of freshly ground pepper and serve.