Peel the potatoes; cut the sides square, and trim off the corners, so as to give an oval shape. With one even cut slice them one eighth of an inch thick the length of the potato; they must be all the same size and shape. Soak them in cold water for half an hour; dry them on a napkin, and fry them in fat which is only moderately hot until they are soft, but not colored. Remove and place them on a sieve to drain and cool. Then immerse them in hot fat, when they will puff into balls. Toss the basket, and remove any that do not puff. Sprinkle with salt, and serve them on a napkin, or as a garnish. Holland potatoes best suit this purpose; it is impossible to get the same result with most of the other varieties.