Everything you love about French onion soup baked together in a scrumptious casserole. A wonderful side dish for any seasonal meal.
Why you will love this
If you love French onion soup - especially the cheesy toasted bread on top - you will love this casserole. It's loaded with chewy sourdough and melty cheese tossed together with sweet caramelized onions.
- Sourdough bread - I love the tangy flavor and chewy texture of sourdough. French bread or Ciabatta can also be used.
- Onions - I always reach for the yellow variety (such as Vidalia) when caramelizing onions, but white or red onion can also be used.
- Gruyere cheese is my favorite for its nutty flavor and good melting quality. Provolone and Fontina are also good options. Use freshly shredded cheese for the best flavor and melting quality.
Please see the recipe card for the complete instructions and ingredient amounts.
- Melt butter over medium heat and add the onions. Stir to coat and cook, stirring occasionally, until softened, 8-10 minutes. (Image 1)
- Meanwhile, preheat oven to 350 degrees and spread bread cubes on a sheet pan. (Image 2).
- Bake for 10-15 minutes until dry and slightly crispy.
- When the onions have softened, add thyme and season with salt and pepper. (Image 3).
- Continue cooking and stirring occasionally until onions have turned golden brown. This will take 30-40 minutes. If the onions start to dry out, add 1-2 tablespoons of water as needed. (Image 4)
- Stir in Worcestershire sauce and vinegar. Taste and adjust salt and pepper as needed.
- Stir in toasted bread cubes. Add the beef broth and toss to combine. The bread should be moist but not soupy. Add more broth if necessary. (Image 5)
- Stir in half of the cheese. Top the casserole with the remaining cheese. (Image 6)
- Bake at 375 degrees for 20-25 minutes until golden brown and cheese is melted. Serve.
- Stir in caramelized mushrooms.
- Add in cooked sausage, bacon, or shredded chicken.
French onion soup is traditionally made with yellow onions and beef broth, while onion soup can include a variety of onions and broths.
The caramelized onions can be made 2-3 days in advance and stored in the refrigerator. You can also toast the bread cubes 2-3 days in advance and store in an airtight container at room temperature. Combine the ingredients when ready to bake.
Other comforting casseroles to try
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French Onion Soup Casserole
- 1 loaf sourdough bread (approx. 14 ounces)
- 4 cups sliced yellow onions (such as Vidalia)
- 3 tablespoons butter
- 1 tablespoon fresh thyme (or 1 teaspoon dried)
- salt and pepper
- 1 teaspoon Worcestershire sauce
- 1 teaspoon white wine vinegar
- ¾ cup beef broth (plus more as needed)
- 8 ounces Gruyere cheese (shredded)
- Preheat the oven to 350 degrees.
- In a large shallow oven-safe skillet over medium heat, melt the butter. Add the onions and toss to coat. Cook, stirring occasionally, until softened, 8-10 minutes.
- Meanwhile, cut the bread into 1-inch cubes. Spread on a half sheet pan and bake for 10-15 minutes until dry and slightly crisp. Set aside. Turn the oven up to 375 degrees.
- When the onions are soft, add the thyme and season with salt and pepper. Continue cooking, stirring occasionally, until golden brown, 30-40 minutes. If the onions dry out, add 1-2 tablespoons of water as needed.
- Stir in Worcestershire sauce and vinegar. Taste and season with salt and pepper as needed. Stir in bread and toss together.
- Add the beef broth and stir to combine. The bread should be moist but not soupy. Add more broth if needed.
- Add half of Gruyere cheese and fold together. Top with the remaining cheese.
- Bake at 375 for 20-25 minutes until golden brown on top. Serve.
- Use freshly shredded cheese for the best flavor and melting quality.
- To make ahead: caramelize the onions up to 2-3 days in advance and store in the refrigerator. Toast the bread cubes up to 2-3 days in advance and store in an airtight container. Combine the ingredients and bake according to the directions.
Nutritional information is an estimate and will vary depending upon the exact amounts and specific ingredients used.