In a large bowl, combine the julienned carrots, apple, sliced radishes, and red onion.
In a small bowl, whisk together the apple cider vinegar, Dijon mustard, and honey (if using).
Slowly whisk in the olive oil until the dressing is emulsified. Season with salt and pepper to taste.
Pour the dressing over the vegetables and toss well to combine.
Let the slaw sit for about 10-15 minutes before serving to allow the flavors to meld.
