In a large bowl, combine the chopped romaine lettuce, cooked bacon, diced chicken, cherry tomatoes, avocado, blue cheese, and chives. Toss gently to mix all the ingredients evenly.
In a separate bowl, whisk together the mayonnaise, buttermilk, red wine vinegar, Dijon mustard, garlic powder, salt, and pepper until smooth and creamy.
Drizzle the dressing over the salad and toss gently to coat all the ingredients.
Serve immediately, or chill in the refrigerator for about 15 minutes to allow the flavors to meld.