1. In a large bowl, whisk together mayonnaise, sour cream, apple cide vinegar, Dijon mustard ann granulated sugar until blended.
2. Add shredded coleslaw mix, julienned radishes and scallions to bowl; toss gently to coat.
3. Season with salt and ground pepper, if desired. Line serving bowl with red cabbage leaf, if desired. Spoon mixture into serving bowl.