Take the same quantity of potatoes and celery. Boil them in salted water and mash them thoroughly well (for safety pass the purée obtained through a hair sieve). The mixture should be then prepared like a potato puree, that is, over the fire so that it gets quite dry, with pieces of butter and hot milk, whipping all the time. Season well and add, mixing quickly one (or two according to quantity) yolks of egg. The mixture should be fairly stiff. Shape it into little balls or quenelles when partly cold, roll them in bread-crumbs and fry them like any croquettes in deep fat. Drain well, of course, before serving.