Toss the cabbage and carrots with 1 teaspoon salt in a colander and let them drain for 20 minutes.

Rinse the vegetables briefly under cold water, then spin or pat them completely dry.

Whisk the mayonnaise, vinegar, sugar, mustard, celery seed, pepper and remaining salt in a large bowl.

Fold the cabbage and carrots into the dressing until evenly coated.

Refrigerate for at least 2 hours, stir once and serve within 24 hours for the best crunch.