Shred the green cabbage into thin 1/8-inch strips, peel and shred the carrots, and coarsely chop the fresh Italian parsley. I find that shredding by hand or with a mandoline gives you better control over thickness than a food processor, which can sometimes make the cabbage too fine and wet. Place all shredded vegetables and chopped parsley in a large mixing bowl.

In a separate medium bowl, combine the mayonnaise, apple cider vinegar, Dijon mustard, celery seeds, fine sea salt, freshly ground black pepper, granulated sugar, and onion powder. Whisk these ingredients together until the dressing is smooth and well-blended, making sure the salt and sugar are fully dissolved. This ensures even seasoning throughout the coleslaw.

Pour the dressing from Step 2 over the vegetable mixture from Step 1 and stir until all the cabbage and carrots are evenly coated. I like to use a sturdy spoon or spatula to gently fold the ingredients together rather than stirring vigorously, which helps keep the vegetables crisp. Refrigerate for at least 1 hour before serving to allow the flavors to meld and the texture to set properly.