Boil potatoes in salted water until soft, approx 10 - 14 minutes, or until soft if pierced with a fork.
Drain and let cool.
While the potatoes are boiling, combine red onion, celery, mustard, olive oil, vinegar and mayonnaise and season with salt and pepper. Mix well and let the flavors marinade while the potatoes cook. Once the potatoes are done and cool, mix into the bowl and add chives and apples, additional salt and pepper to taste. Serve room temperature or refrigerate until ready to serve.
Be sure to pair with a lean protein and fibrous carb.