1. Slice both cabbage halves into 1/8 inch strips. Personally I like to avoid the thick core of the cabbage, to create a more enjoyable mouth feel.
2. Grate carrots, dice green onions and combine with the cabbage mixture.
3. Grate apple and discard core. Lightly coat in the lemon juice to avoid discoloration.
4. In a medium sized bowl, whisk together sour cream, mayonnaise, vinegar, black pepper, celery seed, kosher salt and mustard powder until well combined. Store in the refrigerator until just before serving.
5. Just before serving, add apples to the vegetable mixture and store through half of the dressing. Continue adding dressing a few tablespoons at a time until you have your preferred amount of dressing across your slaw.
6. Serve slaw immediately. This recipe pairs really well with pulled pork either on the side, or right on the sandwich.