Sweet and yukon gold potatoes are the focal point of this gratin that's perfect for the holidays. Fresh parsley and chives deliver a fresh punch that adds an unbeatable flavor. Our favorite casserole cheese, gruyère, tops off the casserole. "This luscious gratin strikes a happy middle chord for those hungry for potatoes and those vying for a sweet potato casserole." --Nancy Vienneau, author of Third Thursday Community Potluck Cookbook, from which this recipe was adapted.