Partially fill large saucepan with cold water. Peel potatoes; cut in quarters & add to pan. Bring to a boil, then reduce heat, cover & simmer briskly about 15 min. or until potatoes are tender. Drain well; place in large bowl & mash coarsely with potato masher or fork. Add salt & 3 tbs. margarine & continue to mash until potaotes are smooth. Mix in enough flour, one tbs. at a time, to form a stiff dough. Preheat griddle or heavy skillet over high heat; grease lightly. Turn dough onto floured surface & knead lightly. Roll out with floured rolling pin to thickness of 1/4 inch. Cut in rounds with 2-inch fluted or plain cookie cutter. Cook on griddle or in skillet 4-5 min. on each side or until golden brown. Serve hot with margarine.