Almost Instant Pierogis
["3 lb. potatoes (about 8), peeled and quartered", "8 oz. sharp Cheddar, shredded (2 c.)", "1 tsp. salt", "1/2 tsp. pepper", "1/2 c. butter or margarine", "6 c. sliced onions", "1 (12 oz.) box jumbo shells, cooked, drained and cooled under cold water"]
["Cook potatoes until tender.", "Drain and return to pot.", "Add cheese to potatoes and mash until cheese melts.", "Stir in salt and pepper.", "Melt butter in large skillet.", "Add onions and cook 10 to 15 minutes, stirring several times until tender, but not browned."]
["potatoes", "Cheddar", "salt", "pepper", "butter", "onions", "jumbo shells"]