Wash and soak two kidneys in a large amount of water, for several hours
or over night, changing the water at least once. Cut them open, rinse
them and put them on to boil in boiling salted water to barely cover
them, in a small cooker-pail. Let them boil five minutes, set the pail
in a larger pail of boiling water, and cook them ten hours or more in a
cooker. When tender, remove the tubes and membranes and slice the
kidneys. Thicken as much of the gravy as you wish to use, with
one-fourth of a cupful of flour mixed with one-fourth of a cupful of
water to each pint of gravy. Add the sliced kidneys and serve them when
they are boiling hot.