Scalloped Potatoes
["2 lb. potatoes (about 6 medium)", "1/4 c. finely chopped onion", "3 Tbsp. flour", "1 tsp. salt", "1/4 tsp. pepper", "1/4 c. butter and margarine", "2 1/2 c. milk"]
["Heat oven to 350\u00b0.", "Wash potatoes; pare thinly and remove eyes.", "Cut potatoes into thin slices to measure about 4 cups."]
["potatoes", "onion", "flour", "salt", "pepper", "butter", "milk"]