Old-Fashioned Scalloped Potatoes
["3 Tbsp. butter or margarine", "3 Tbsp. all-purpose flour", "1 1/2 tsp. salt", "1/4 tsp. pepper", "3 lb. medium potatoes", "2 Tbsp. minced onions", "3 c. milk"]
["Peel potatoes with sharp knife; thinly slice potatoes.", "In greased 2-quart casserole, arrange half the potatoes.", "Sprinkle with half the onion; pour half the sauce on top.", "Repeat with remaining potatoes."]
["butter", "flour", "salt", "pepper", "potatoes", "onions", "milk"]