Description
The french onion soup casserole recipe is essentially a deconstructed and “sturdier” version of the classic soup. In a traditional soup setting, you have a deep bowl of broth with a single crouton and a layer of cheese on top. In the casserole version, we shift the ratios to make it more of a cohesive meal. We use a higher concentration of onions and a slightly thickened sauce, topped with a generous layer of baguette slices that act as a platform for a massive amount of melted Gruyere and Parmesan.
Ingredients
- 4 large onions, thinly sliced
- 3 tbsp butter
- 1 tbsp olive oil
- 3 cloves garlic, minced
- 1 tsp sugar (helps caramelize onions)
- 1 tsp salt
- ½ tsp black pepper
- 1 tsp thyme (dried or fresh)
- 2 tbsp all-purpose flour
- 3 cups beef broth
- ½ cup white wine (optional)
- 1 tbsp Worcestershire sauce
- 1 baguette, sliced
- 2 cups shredded Gruyère or mozzarella cheese
- ½ cup parmesan cheese
Instructions
- Caramelize onions
In a large pan, heat butter + olive oil. Add onions, salt, and sugar. Cook on low heat for 25–30 minutes until deep golden brown. - Add garlic & seasoning
Stir in garlic, thyme, and pepper. Cook for 1–2 minutes. - Thicken mixture
Sprinkle flour over onions and stir well. - Add liquids
Slowly pour in broth, wine (if using), and Worcestershire sauce. Simmer for 10 minutes until slightly thickened. - Assemble casserole
Preheat oven to 375°F (190°C). Transfer onion mixture to a baking dish. - Add bread & cheese
Layer baguette slices on top, then cover with Gruyère and parmesan. - Bake
Bake for 15–20 minutes until cheese is melted and golden. - Serve
Let it cool slightly before serving.
Notes
This casserole turns classic French onion soup into a warm, cheesy bake that’s perfect for comfort food nights.
- Prep Time: 20 minutes
- Cook Time: 45 minutes
- Category: Main Dish
- Method: Baking
- Cuisine: French
Nutrition
- Serving Size: 1 portion
- Calories: ~380 kcal
Keywords: baked french onion soup, french onion casserole with bread, cheesy onion bake, slow cooked onion casserole, easy onion soup gratin casserole