Oil and Vinegar Coleslaw

I like oil and vinegar slaw way better than the mayo kind - if you haven't tried it, you need to!

1/2 head green cabbage, cored and thinly sliced
1/2 head purple cabbage cored and thinly sliced
1 medium onion, thinly sliced
1 1/2 cups shredded carrots
2 teaspoons kosher salt
1 teaspoon freshly cracked white pepper
1 cup apple cider vinegar
1 cup sugar
1 teaspoon dry mustard powder
2 teaspoons celery seeds
1/2 cup vegetable oil
1/4 cup finely chopped green onion tops

In a large, non-reactive bowl, combine the cabbage, onion and carrot, season with the salt and pepper and cover with plastic wrap. Refrigerate for 1 hour before proceeding.

Meanwhile, combine the vinegar, sugar, mustard and celery seeds in a small saucepan and bring to a boil. Stir the vinegar periodically to dissolve the sugar. Once the sugar is dissolved, remove from the heat. Remove the cabbage from the refrigerator and pour the vinegar over the top of the cabbage. Add the oil and green onions and toss well to thoroughly combine.

Cover with plastic wrap and return the cabbage to the refrigerator. Allow slaw to sit for 2 or 3 hours before serving, stirring occasionally.