Prepare the vegetables. Start by shredding the green and red cabbage into thin, uniform slices. If you prefer a sweeter slaw, you can add shredded carrots, but remember to use them in moderation due to their carb content. Place the shredded vegetables into a large mixing bowl.
Create the dressing. In a separate small bowl, whisk together the mayonnaise, apple cider vinegar, Dijon mustard, lemon juice, powdered erythritol, salt, and pepper. Adjust the seasoning according to your taste preferences. Remember, you can always add more seasoning later if needed.
Combine and toss. Pour the dressing over the shredded vegetables and parsley. Using tongs or a large spoon, gently toss the mixture until the vegetables are evenly coated with the sauce. Ensure that every bite is infused with the flavors of the dressing.
Chill and marinate. Cover the bowl with plastic wrap or transfer the coleslaw to an airtight container. Place it in the refrigerator to chill for at least 30 minutes. This will allow the flavors to meld together and for the cabbage to slightly soften.
Serve and enjoy. Once chilled, your keto coleslaw is ready to be enjoyed!