# French Onion Broccoli Cheese Casserole
A rich and creamy casserole blending the savory, umami depth of classic French onion soup with tender broccoli florets and a decadent blend of Gruyère and sharp white cheddar cheeses.
Equipment
- Large skillet or Dutch oven
- 9x13 inch Casserole Dish
- Medium saucepan
- Whisk
Ingredients
For the French Onions
- 4 tablespoons unsalted butter
- 2 large yellow onions thinly sliced
- 1/2 cup beef broth
- 1 teaspoon dried thyme
- 1 tablespoon Worcestershire sauce
For the Casserole Base and Sauce
- 2 (10 ounce) bags frozen broccoli florets thawed and drained well
- 4 tablespoons unsalted butter
- 1/4 cup all-purpose flour
- 2 cups whole milk
- 1 cup beef broth remaining from onion preparation
- 1/2 teaspoon salt
- 1/4 teaspoon black pepper
- 1 1/2 cups shredded Gruyère cheese divided
- 1 cup shredded sharp white cheddar cheese
For the Topping
- 1 (6 ounce) container French Fried Onions divided
Instructions
Prepare the French Onions
- Melt 4 tablespoons of butter in a large skillet or Dutch oven over medium-low heat. Add the sliced yellow onions and cook, stirring occasionally, for 15 to 20 minutes, until deeply golden brown and caramelized.
- Increase the heat to medium and pour in the 1/2 cup of beef broth and the Worcestershire sauce, scraping the bottom of the pan to lift any browned bits (deglazing). Stir in the dried thyme. Set the onions aside.
Prepare the Base and Sauce
- Preheat oven to 375°F (190°C). Lightly grease a 9x13 inch casserole dish. Place the drained broccoli florets into the prepared casserole dish.
- In a separate medium saucepan, melt the remaining 4 tablespoons of butter over medium heat. Whisk in the flour and cook for 1 minute, stirring constantly, until a smooth paste (roux) forms. Gradually whisk in the 2 cups of whole milk until the mixture is smooth.
- Bring the milk mixture to a gentle simmer, whisking frequently. Once the sauce has thickened slightly, reduce the heat to low. Stir in the remaining 1 cup of beef broth, salt, and black pepper. Remove the pan from the heat.
- Stir in 1 cup of the Gruyère cheese and all of the sharp white cheddar cheese until completely melted and the sauce is smooth. Pour the prepared caramelized French onions and their liquid into the cheese sauce. Stir well to combine.
Assembly and Baking
- Pour the entire cheese and onion mixture over the broccoli in the casserole dish. Gently stir the mixture to ensure the broccoli is evenly coated.
- Sprinkle the remaining 1/2 cup of Gruyère cheese evenly over the top of the casserole. Scatter half (about 3 ounces) of the French Fried Onions over the cheese layer.
- Bake for 20 to 25 minutes at 375°F, or until the casserole is bubbly and the cheese is melted.
- Remove the casserole from the oven. Increase the oven temperature to 400°F (200°C). Scatter the remaining French Fried Onions over the top. Return the casserole to the oven and bake for an additional 3 to 5 minutes, or until the topping is golden brown and crisp.
- Allow the casserole to rest for 5 to 10 minutes before serving.
Notes
For a richer flavor, consider using fresh thyme instead of dried. If you prefer a milder cheese flavor, substitute the sharp white cheddar with mozzarella or Provolone, which melt beautifully but lack the necessary tang to cut through the richness of the French onions.