How to Make It
Place potatoes in a large Dutch oven with cold water to cover by 2 inches. Bring to a boil over medium-high; boil until potatoes are tender, about 25 minutes. Drain and return potatoes to Dutch oven over medium. Cook, stirring once, until potatoes dry out slightly, 30 to 50 seconds.
Place buttermilk and butter in a microwavable glass bowl, and microwave on HIGH until warm, 30 to 60 seconds. Add warm buttermilk mixture, cream cheese, Parmesan, salt, and white pepper to potatoes, and coarsely mash with a potato masher to desired consistency. Sprinkle with chives just before serving.
Spoon potatoes into a 4- to 6-qt. slow cooker. Cover and cook on HIGH until heated through, about 2 hours. Or reheat in a tightly covered baking dish at 350°F until heated through, about 1 hour.