This French onion casserole recipe takes all the delicious, comforting elements of French onion soup and turns them into a side dish you can put on a plate, perfect next to homey braised beef or casual roast beef sliders. Silky, caramelized onions are tossed with flour and butter to make a rich sauce, then topped with croutons and layers of melted cheese.

Ingredients for French Onion Casserole

• Onions: A generous amount of onions are sliced thin and cooked until very tender.
• Butter: Cooking onions in butter allows them to become soft and slightly golden, and delivers luxurious flavor.
• Flour: All-purpose flour melts together with butter and broth to thicken the sauce.
• Beef broth: Store-bought or homemade beef broth brings the flavors of French onion soup together for this casserole.
• Sherry: This fortified wine is a secret ingredient that adds a sweet, nutty complexity to this dish, and it’s also great in other soups like split pea soup or mushroom soup. If you’d prefer not to use any alcohol, you can also use additional beef broth.
• Croutons: Salad croutons are a simple way to top this dish with bread, and they hold up well to the sauce and melted cheese.
• Swiss cheese: Nutty, shredded Swiss cheese melts beautifully (Gruyere or a young comté are good substitutes).
• Parmesan cheese: Grated Parmesan cheese doesn’t melt, but it adds a lot of flavor to the cheese topping.

Taste of Home