Scalloped Potato Casserole
["3 Tbsp. butter", "2 Tbsp. all-purpose flour", "3 c. milk", "6 medium potatoes, pared and thinly sliced", "1/2 tsp. black pepper", "1 1/2 tsp. salt", "2 Tbsp. chopped onion"]
["Make white sauce with first 4 ingredients and pepper.", "Place half of potatoes in 2-quart casserole dish, cover with 1/2 of the onions and then 1/2 of the sauce.", "Repeat layers.", "Cover and bake at 350\u00b0 about 1 hour.", "Uncover and bake 30 minutes longer."]
["butter", "flour", "milk", "potatoes", "black pepper", "salt", "onion"]