- Combine the cabbage and carrots in a large bowl and toss with the sugar and kosher salt. Let rest for 5 minutes, then transfer to a colander and rinse thoroughly with cold water. (Not thoroughly rinsing the cabbage will result in overly salty slaw.)
- Rinse and dry the bowl. Run the cabbage and carrots through a salad spinner to remove the excess moisture, or spread out the mixture on a clean kitchen towel and pat dry with paper towels or another kitchen towel.
- Once dry, return the mixture to the bowl and add the green onions. In a small bowl, mix together the mayonnaise, vinegar, maple syrup, mustard, parsley, celery seed, and pepper.
- Once thoroughly combined, add the dressing to the cabbage mixture and toss until evenly coated. Add salt if needed. Chill for at least 30 minutes before serving. Leftovers will keep in an airtight container in the fridge for 2 to 3 days.