This broccoli au gratin is creamy, cheesy, and topped with a crisp, buttery breadcrumb layer that gives it a cozy, casserole-style finish. Tender broccoli is coated in a rich cheese sauce with white Cheddar and Gruyère, then broiled until bubbling and golden on top.

Why You’ll Love This Recipe

This recipe turns simple broccoli into a comforting side dish that feels special enough for holidays but easy enough for a family dinner. The combination of two cheeses gives the sauce both sharpness and nuttiness, while the mustard and garlic add extra depth without overpowering the broccoli. The panko topping brings the kind of crunchy finish that makes every bite more satisfying. It is also a great make-ahead option, which is helpful when you are planning a bigger meal.

Ingredients

(Tip: You’ll find the full list of ingredients and measurements in the recipe card below.)

• 2 (12-ounce) packages fresh broccoli florets, about 8 cups
• 3 tablespoons unsalted butter, divided
• 1/2 cup chopped onion
• 1 tablespoon chopped garlic
• 1/4 cup all-purpose flour
• 2 3/4 cups reduced-fat milk, at room temperature
• 1 teaspoon dry mustard
• 1 teaspoon Dijon mustard
• 1/4 teaspoon salt, plus 1/8 teaspoon, divided
• 1/4 teaspoon ground black pepper
• 1/8 teaspoon cayenne pepper, optional
• 3/4 cup shredded sharp white Cheddar cheese, divided
• 3/4 cup shredded Gruyère cheese, divided
• 1/4 cup panko breadcrumbs
• 1/4 teaspoon salt-free garlic-and-herb seasoning
• cooking spray, for the baking dish

Directions

1. Preheat the oven to broil and position a rack in the top third of the oven. Lightly coat a 7 x 11-inch broiler-safe baking dish with cooking spray.
2. Bring a large pot of water to a boil over high heat. Add the broccoli florets and cook for 5 to 6 minutes, stirring occasionally, until tender and bright green. Drain well.
3. Transfer the broccoli to the prepared baking dish and spread it into an even layer.
4. In a medium saucepan, melt 2 tablespoons of the butter over medium heat. Add the chopped onion and cook for 3 to 4 minutes until softened. Stir in the garlic and cook for 30 seconds more.
5. Sprinkle in the flour and whisk continuously for about 1 minute to form a smooth roux.
6. Gradually pour in the milk, whisking constantly to keep the sauce smooth. Add the dry mustard, Dijon mustard, 1/4 teaspoon salt, black pepper, and cayenne pepper if using.
7. Continue cooking, whisking often, until the sauce thickens enough to coat the back of a spoon, about 4 to 6 minutes.
8. Remove the pan from the heat. Stir in 1/2 cup of the white Cheddar and 1/2 cup of the Gruyère until melted and smooth.
9. Pour the cheese sauce evenly over the broccoli.
10. In a small bowl, combine the panko breadcrumbs, garlic-and-herb seasoning, the remaining 1 tablespoon butter melted, the remaining 1/4 cup white Cheddar, the remaining 1/4 cup Gruyère, and the remaining 1/8 teaspoon salt.
11. Sprinkle the breadcrumb mixture evenly over the top of the broccoli and sauce.
12. Broil for 2 to 4 minutes, watching carefully, until the topping is golden brown and the sauce is bubbling around the edges.
13. Let the dish rest for a few minutes before serving.

Servings and timing

This recipe makes about 6 servings.

Prep time: 15 minutes
Cook time: 30 minutes
Total time: 45 minutes

Variations

For a richer version, use whole milk instead of reduced-fat milk. You can also swap the white Cheddar for regular sharp Cheddar if that is what you have on hand. For a more pronounced nutty flavor, increase the Gruyère slightly and reduce the Cheddar a bit. If you want a little extra texture, add a spoonful of grated Parmesan to the breadcrumb topping. To make it more filling, stir in cooked cauliflower with the broccoli for a mixed vegetable gratin.

Storage/Reheating

Store leftovers in an airtight container in the refrigerator for up to 3 days. For the best texture, reheat in a 350°F oven until warmed through, about 15 to 20 minutes. You can cover it loosely with foil at first, then uncover it for the last few minutes to help the topping crisp up again. Microwave reheating works too, but the breadcrumb topping will be softer.

FAQs

Can I use frozen broccoli instead of fresh?

Yes, but thaw it first and drain it very well so the gratin does not become watery. Patting it dry with paper towels helps even more.

What does au gratin mean?

Au gratin refers to a dish topped with a browned crust, usually made with cheese, breadcrumbs, or both. In this recipe, the crunchy topping is one of the best parts.

Can I make this recipe ahead of time?

Yes. You can blanch the broccoli, make the sauce, assemble the dish, and refrigerate it before broiling. Add the topping just before baking or broiling for the best texture.

Why is my cheese sauce too thick?

This usually happens when the sauce cooks too long. Add a splash of milk and whisk until it loosens to the consistency you want.

Why is my sauce too thin?

The sauce may need a little more time on the stove to thicken. Keep whisking over medium heat until it coats the back of a spoon.

Can I use only one type of cheese?

Yes. The flavor will be slightly different, but using all white Cheddar or all Gruyère will still give you a delicious result.

What should I serve with broccoli au gratin?

It pairs well with roasted chicken, grilled beef, baked fish, or a simple rice dish. It also works nicely as part of a holiday spread.

How do I keep the topping crisp?

Broil it just until golden and do not cover the dish tightly while it is still hot. Reheating in the oven instead of the microwave also helps preserve the crunch.

Can I add more seasoning?

Absolutely. A pinch of paprika, a little onion powder, or extra black pepper can all work well without changing the recipe too much.

Is this recipe good for holidays?

Yes, it is an excellent holiday side dish because it feels comforting and classic while still being easy to prepare. The golden topping also makes it look especially inviting on the table.

Conclusion

Broccoli au gratin is one of those side dishes that makes vegetables feel every bit as satisfying as the main course. With tender broccoli, a silky cheese sauce, and a crisp breadcrumb topping, it brings together comfort, flavor, and texture in every spoonful. Whether you serve it for a weeknight dinner or a festive gathering, this dish is a reliable crowd-pleaser that is easy to come back to again and again.

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