Trim the leeks, and remove the coarse tops and outer skin. Cut into 3 in / 7.5 cm. lengths, and slice in half lengthways. Shred the leeks into long, thin strips. Rinse and dry them thoroughly. Put oil in a wok or deep frying pan to a depth of about 3 in / 7.5 cm, and heat until a cube of bread sizzles as soon as it is dropped in. Fry the leeks in batches for about 20 seconds each, and drain them on kitchen paper before serving.