French Onion Soup Casserole

French Onion Soup Casserole 8 medium onions, sliced 5 Tbsp. butter, divided 2 Tbsp. all-purpose flour Dash pepper 3/4 cup beef broth 1/4 cup sherry or additional beef broth 1-1/2 cups salad croutons 1/2 cup shredded Swiss cheese 3 Tbsp. grated Parmesan cheese In a large skillet, saute onions in 3 Tbsp. butter until tender. Stir in flour and pepper until blended; gradually add broth and sherry. Bring to a boil; cook and stir for 3 minutes or until thickened. Transfer onto an ungreased 9" square baking pan. In a microwave, melt the remaining butter. Add the croutons; toss to coat. Spoon over the onion mixture. Sprinkle with cheeses. Broil 3-4" from heat for 1-2 minutes or until cheese is melted.