In a large bowl, combine the shredded cabbage and grated carrots.
In a separate bowl, whisk together the mayonnaise, sour cream, apple cider vinegar, sugar, celery seeds, ground mustard, salt, and pepper until well combined.
Pour the dressing over the cabbage and carrots, and toss until all the ingredients are evenly coated.
Cover the bowl and refrigerate for at least 1 hour to allow the flavors to meld together.
Before serving, give the coleslaw a good stir and adjust the seasoning if needed.
Serve chilled as a side dish with your favorite main course.