Whisk together the sour cream and mayo. Stir in the lemon juice and milk. Finally, stir in the black pepper and blue cheese. Place dressing in fridge for at least 30 minutes, or until ready to use.
For the iceberg wedge salad:
Cook the bacon strips until crisp and remove to a paper towel lined plate to drain. Crumble when cool enough to touch and set aside.
Place ¼ of the iceberg lettuce on a plate and pour a few tablespoons of blue cheese dressing over the wedge. Top with crumbled bacon, red onions, tomatoes, and blue cheese. If using, sprinkle parsley or scallions over the top. Serve salads immediately.
Notes
*Homemade blue cheese dressing will keep in a jar in the fridge for up to seven days.