Cheesy Cauliflower au Gratin

published Oct 8, 2022
Cauliflower au Gratin Recipe

Cauliflower baked in a creamy, cheesy sauce with a buttery, crisp topping.

Serves6 to 8

Prep20 minutes

Cook20 minutes

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A photo of a tray of baked Cauliflower au gratin.
Credit: Laura Manzano

When you want to eat your vegetables but crave the comfort that only a creamy, cheesy sauce provides, cauliflower au gratin is your answer. This recipe makes clever use of your microwave and turns cauliflower into a decadent side dish — just in time for the holidays. 

How Stop Cauliflower au Gratin from Becoming Watery

The secret to thick and creamy au gratin? Béchamel. The trick is to make this butter-, flour-, and milk-based mother sauce thicker than you think you should. The standard ratio of butter to flour for a béchamel is one to one, but we tweak it just a bit to make the sauce as thick as it can be. The cauliflower will release moisture as it continues to cook, thinning out the sauce slightly to result in the perfect texture.

Credit: Laura Manzano

The Microwave Is Your Friend

The microwave is often relegated to just reheating leftovers and melting butter, but when used correctly, it can be your secret weapon in the kitchen. In this case, par-cooking the cauliflower in the microwave before topping it with sauce means it only needs a few minutes in the oven to get bubbly and golden. Without par-cooking, your cauliflower would still be crunchy! Microwaves require no additional moisture to steam the cauliflower to fork-tenderness, and it only takes a few minutes with no additional burners or heat. 

What Other Vegetables Can Be Made au Gratin? 

The brassica family really shines in this application, but feel free to use any vegetable that doesn’t release too much moisture. A few of our favorites are as follows:

Cauliflower au Gratin Recipe

Cauliflower baked in a creamy, cheesy sauce with a buttery, crisp topping.

Prep time 20 minutes

Cook time 20 minutes

Serves 6 to 8

Nutritional Info


  • 2 1/2 pounds


  • 3 teaspoons

    kosher salt, divided, plus more for seasoning

  • 1 teaspoon

    freshly ground black pepper, divided, plus more for seasoning

  • 1/2

    large yellow onion

  • 6 large cloves


  • 6 ounces

    Gruyère cheese

  • 6 ounces

    sharp cheddar cheese

  • 8 tablespoons

    unsalted butter, divided

  • 3 sprigs

    fresh thyme

  • 1 tablespoon

    Dijon mustard

  • 1/2 cup

    all-purpose flour

  • 3 cups

    whole milk

  • 1 cup

    panko breadcrumbs


  1. Cut 2 1/2 pounds cauliflower into rough 1-inch florets. Place in a large microwave-safe bowl and cover with a damp paper towel. Microwave on HIGH until the cauliflower is fork tender but not mushy, 5 to 7 minutes. Transfer to a 9x13-inch baking dish. Season with 2 teaspoons of the kosher salt and 1/2 teaspoon of the black pepper and toss to combine. Arrange into an even layer.

  2. Arrange a rack in the middle of the oven and heat the oven to 450ºF. Meanwhile, dice 1/2 large yellow onion until you have 1 cup. Thinly slice 6 large garlic cloves. Grate 6 ounces Gruyère cheese and 6 ounces sharp cheddar cheese on the large holes of a box grater (about 1 1/2 cups each).

  3. Melt 5 tablespoons of the unsalted butter in a medium saucepan over medium-high heat. Add the onion, garlic, 3 fresh thyme sprigs, and remaining 1 teaspoon kosher salt. Cook, stirring occasionally, until the onion and garlic are softened and translucent, 5 to 7 minutes. Add 1 tablespoon Dijon mustard and cook for 30 seconds. Sprinkle with 1/2 cup all-purpose flour. Cook, stirring constantly, until the flour is slightly toasted, about 30 seconds.

  4. While whisking constantly, slowly pour in 3 cups whole milk. Add the Gruyère, cheddar, and remaining 1/2 teaspoon black pepper. Stir and cook until the cheese is melted and the sauce is bubbling, about 5 minutes. Remove and discard the thyme sprigs. Pour the sauce evenly over the cauliflower.

  5. Place the remaining 3 tablespoons unsalted butter in a small microwave-safe bowl. Microwave on HIGH until melted, about 30 seconds. Add 1 cup panko breadcrumbs and season with a pinch each of kosher salt and black pepper. Stir with a fork or mix with your fingertips until the panko is evenly moistened. Sprinkle evenly over the cauliflower.

  6. Bake until the sauce is bubbling and the panko is golden brown, 10 to 15 minutes. If you’d like a browner top, broil for 2 to 3 minutes more. Let cool for 10 minutes to let the sauce thicken before serving.

Recipe Notes

Make ahead: The sauce can be made up to 2 days ahead, cooled, and refrigerated in an airtight container. The cauliflower can be microwaved and refrigerated up to 2 days ahead. Bring the sauce back to a simmer over medium heat before proceeding with the recipe.

Storage: Leftovers can be refrigerated in an airtight container for up to 4 days.