SCALLOPED POTATOES FOR FIFTY Loretta McFeaters

22 lb. potatoes, peeled and sliced 1/4 lb. butter
3 qt. milk 3 to 4 tsp. salt
3 cans mushroom soup 1 medium onion, minced
pepper, optional

Heat potatoes in a small amount of water. Heat milk, soup; add butter, salt, and pepper. Add onion. Drain potatoes, place in large greased roaster. Pour milk mixture over all. Bake at 325 degrees for about 1 1/2 hours.