Bake the potatoes in their skins at least 24 hours before using; 36 hours does even better. Keep them in the refrigerator. Peel them, cut in cubes, and put in the top of a double boiler covered with the cream and salt to taste. Cook uncovered for an hour. Place the potatoes and cream in a low casserole and dot with butter, sprinkle with grated cheese and paprika and cook in a 325 to 350 degrees F oven for another half hour.