French Onion Soup
["1 1/2 lb. onions, sliced thin", "1/4 c. butter", "3 (10 oz.) cans beef broth", "1/4 tsp. salt and pepper", "1 tsp. Worcestershire sauce"]
["Cook onions in butter for 20 minutes; add broth and Worcestershire sauce.", "Bring to a boil.", "Season with salt and pepper."]
["onions", "butter", "beef broth", "salt", "Worcestershire sauce"]