Place whole pork tenderloin into a slow cooker. Arrange potatoes around pork. Cover the pork and potatoes with the sauerkraut and juices. Add 1 cup water, butter. Add salt and pepper to taste.
Many families prepare pork and sauerkraut, typically for hours in a slow cooker or roasted in the oven. Recipes vary and call for ingredients such as apples, beer, applesauce, pepper, sugar ...