French Onion Soup Casserole
A heartwarming casserole that transforms classic French onion soup into layered goodness with caramelized onions, gooey cheese, and crunchy bread.
Ingredients
For the Casserole
- 4 large large onions (yellow or white) Sweet varieties work best for caramelization.
- 4 tablespoons butter Unsalted, for that rich, nutty flavor.
- 1 tablespoon olive oil Adds depth and complexity.
- 6 cups beef broth Homemade or good quality store-bought.
- 1 teaspoon fresh thyme Or ½ teaspoon dried thyme.
- to taste Salt and pepper Elevates all flavors.
- 2 cups Gruyère cheese Feel free to substitute with Swiss if you prefer.
- 1 cup shredded mozzarella cheese For that gooey, cheesy topping.
Instructions
Preparation
- In a large skillet, melt the butter and olive oil over medium heat. Add the sliced onions and a pinch of salt. Allow them to simmer, stirring occasionally, for about 30 minutes until they become golden and sweetly aromatic.
- Pour in the beef broth and thyme. Bring the mixture to a gentle simmer, letting the flavors meld together for about 10 minutes. Season with salt and pepper.
- While the broth concocts magic, slice the baguette into thick rounds. Toast them lightly in the oven at 350°F until they are golden brown.
Assembly and Baking
- Preheat your oven to 375°F. In a large baking dish, layer half of the caramelized onions. Top with half of the toasted bread slices, followed by half of the Gruyère cheese. Repeat these layers—onions, bread, cheese.
- Pour any remaining broth over the assembled layers, allowing it to soak into the bread. Top with the mozzarella cheese.
- Pop the dish into the preheated oven for about 25 minutes, or until the cheese is bubbly and golden brown.
Notes
For a lighter option, swap beef broth for vegetable broth. Store leftovers in an airtight container in the refrigerator for up to three days. Reheat in the oven at 350°F. Quality cheese and broth elevate the dish.