In a large mixing bowl, combine shredded chicken, chopped onions, and dill pickles.

In a separate bowl, whisk together Greek yogurt and mayonnaise until smooth. Add relish, mustard, chives, dill, salt, and pepper.

Pour the dressing over the chicken and vegetable mixture and fold gently to combine.

Taste and adjust seasoning with salt and pepper if needed.

Cover and refrigerate for at least 2 hours to let the flavors meld.

Serve on croissants, in lettuce cups, or with crackers.