To a medium bowl, add the Brussels sprouts and apple; gently toss together. In a small bowl, combine the apple cider vinegar, olive oil, mustard, a few pinches of salt and pepper and a pinch of ground ginger. Whisk together using a fork. Add to the apple and Brussels mixture and toss, making sure it's evenly coated. Give it a taste and adjust the salt and pepper accordingly. Serve as a side or on top of pulled pork sandwiches.