In a large mixing bowl, combine the mayonnaise, dill pickle brine, and dijon mustard. Whisk until the dressing is smooth and well blended.
Stir in the garlic powder, salt, and black pepper.
Add the shredded cooked chicken breast to the bowl and toss thoroughly so every strand is coated in the tangy dressing.
Fold in the finely diced dill pickles and red onion. Mix gently until they are evenly distributed throughout the salad.
Sprinkle in the chopped fresh dill and fold it through one final time.
Cover and refrigerate for at least 30 minutes before serving. The salad tastes even better after an hour or two as the pickle flavor deepens. Serve on bread, crackers, or lettuce cups.