Take some potatoes (the long Dutch kind) and cut them in thin slices (they should not be thicker than two half-a-crown pieces together); wipe them well. Drop them in the hot fat, not too many at the time; they must not stick together. Cook them three-quarters of the full time they ought to cook (by that time usually they come up and float on the top); then take them out. Leave the fat on the fire for two minutes more (it must reach that point when it begins to smoke); put them in again for a minute or two in a wire basket, and they will puff up at once. Make them a good colour, drain well, sprinkle with salt and serve quickly.