The potatoes must be hot and floury, but either eating apples or cooking apples can be used. (Best results with a cooking apple, though.) - Boil the peeled potatoes in well-salted water. Drain and cover with a cloth to "dry in their steam". Sieve or rice into a warmed mixing bowl, and beat in the fat. Work in sufficient flour to make the dough manageable, adding salt to taste. Divide the dough in half and roll or pat into 2 rounds of equal size just over 1/2 inch thick. Place one round on the warmed bakestone and spread with the chopped apple. Cover with the other round of dough and pinch the edges together. - Bake on the bakestone over a moderate heat until brown underneath. Turn using the broadest spatula you have, or two spatulas and a friend. Cook the other side. Remove the cake to a hot serving dish. Carefully peel up one side of the top of the cake, spread the apples with the softened butter, and sprinkle them with sugar. Fold that half down and do the same to the other side. Sprinkle sugar on top, and serve immediately, with thick cool cream.