This cauliflower au gratin recipe is crazy good comfort food! Tender pieces of steamed cauliflower get baked in a creamy and savory sauce flavored with Gruyere and garlic. The whole dish gets topped with cheesy, buttery breadcrumbs and baked until golden brown and bubbly.

saucy cauliflower in an oval baking dish topped with breadcrumbs

Why I Love this Recipe

I’m not usually someone who loves a cheesy-coated vegetable, but this recipe is different. It features quality cheese (Gruyère and Parmesan) and keeps the rest of the flavors relatively simple. Cayenne adds some heat while grated fresh nutmeg highlights the flavors of the cheeses. And finally, thyme and garlic add some welcome savorines to bring it all together.

saucy cauliflower in an oval baking dish topped with breadcrumbs

Ingredients in Cauliflower Gratin

Kosher salt and black pepper are assumed ingredients. 

  1. Cauliflower, one large head is ideal. Seek out one that’s at least 2 pounds in weight.  
  2. Unsalted butter, I keep the amount of butter relatively low, just 4 tablespoons. For a more decadent filling, you can use 4 tablespoons in the roux. 
  3. Onion, yellow or white work well here. You’ll need just one small onion.
  4. Garlic, fresh garlic is always best. 
  5. All-purpose flour is used to make the sauce.
  6. Whole milk 
  7. Nutmeg, grated fresh nutmeg adds the best flavor, but pre-ground also works. 
  8. Cayenne pepper, if you don’t have cayenne you can add red pepper flakes or additional black pepper.
  9. Gruyère can be found in the specialty cheese section. It’s savory and nutty.
  10. Parmesan cheese can also be found in the specialty cheese section. I recommend getting a block and shredding it yourself. 
  11. Whole-wheat Panko, if you can’t find whole-wheat Panko regular Panko works just fine.
  12. Thyme, fresh adds the best flavor but dried will work in a pinch.

How to Make Cauliflower au Gratin

  1. Steam or blanch the cauliflower florets (I like to steam in the microwave because it’s quick and easy).
  2. Cook the onions and garlic in butter until softened.
  3. Whisk in the flour, salt, pepper, cayenne, and nutmeg and cook 2 minutes, whisking constantly.
  4. Gradually whisk in the warmed milk and cook, whisking constantly, until the sauce has thickened. 
  5. Remove the sauce from heat then stir in the Gruyère cheese and half of the Parmesan until melted. 
  6. Add the cauliflower and toss with the cheese sauce to coat. 
  7. Transfer the cauliflower to a baking dish or casserole dish. 
  8. Mix together bread crumbs, melted butter, half of the Parmesan and thyme. Sprinkle the breadcrumb topping over the au gratin. 
  9. Bake cauliflower au gratin until golden brown and bubbly.
bread crumb-topped casserole in an oval baking dish

FAQs & Test Kitchen Tips

Can I substitute anything for the Gruyère?

You can use more Parmesan or try using a sharp Cheddar. Aged Gouda would also be delicious.

Can I make this ahead of time?

I would not make the entire dish ahead of time, but you can prep the components. Steam the cauliflower and make the cheese sauce up to 3 days ahead of time. On the day-of, reheat the cheese sauce on the stovetop in a saucepan over low heat. Toss the sauce with the cauliflower and finish the dish per the recipe instructions.

More Side Dish Recipes to Love…

If you make this cauliflower gratin recipe leave a comment with a star rating below, I love hearing from you!

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bread crumb-topped casserole in an oval baking dish

Cauliflower au Gratin with Gruyere & Thyme

  • Author: Lauren Grant
  • Prep Time: 10 minutes
  • Cook Time: 40 minutes
  • Total Time: 50 minutes
  • Yield: 6 servings 1x
  • Category: Side dish
  • Method: Baking
  • Cuisine: American/French
  • Diet: Vegetarian

Description

A creamy and cozy cauliflower au gratin. Flavored with Gruyère, Parmesan, and fresh thyme, it’s simple yet spectacular.


Ingredients

Scale
  • 1 large head cauliflower (22 ½ pounds), cut into 1-inch florets
  • 4 tablespoons unsalted butter, divided
  • 1 cup diced onion
  • 2 large cloves garlic, minced
  • 3 tablespoons all-purpose flour or regular whole-wheat flour
  • 1 ½ cups whole milk, warmed
  • Kosher salt and black pepper
  • ½ teaspoon freshly grated nutmeg
  • ¼ teaspoon cayenne pepper
  • ½ cup shredded Gruyère (2 ounces)
  • ½ cup shredded Parmesan (2 ounces), divided
  • ½ cup whole-wheat Panko breadcrumbs 
  • 2 teaspoons chopped fresh thyme, or 1 teaspoon dried

Instructions

  1. Preheat oven to 425°F (218ºC). Coat a 2-quart baking dish with nonstick spray.
  2. Place cauliflower florets in a large glass bowl. Add 1 tablespoon water and ¼ teaspoon salt; toss to coat then place a large dinner plate over top (or cover tightly with a piece of plastic wrap). Microwave for 2 minutes, stir and continue to microwave in 1 minute intervals until crisp-tender, about 4–5 minutes total*. Drain and set aside.
    cauliflower florets in a glass bowl with a white plate set on top
  3. Melt 2 tablespoons butter in a large sauté pan over medium heat. Add onions and garlic and cook until softened, about 5 minutes.
    onions cooked in a skillet with butter
  4. Whisk in flour, ½ teaspoon each salt and black pepper, nutmeg, and cayenne and cook, whisking constantly, 2 minutes.
    onions cooking in a skillet with spices
  5. Slowly whisk in milk until thickened, 2 minutes. Off heat, stir in Gruyère and ¼ cup Parmesan, then stir in cauliflower until completely coated; transfer to prepared baking dish.
    cauliflower in a pan coated with cheese sauce
  6. Melt remaining 2 tablespoons butter. Combine melted butter with Panko, remaining ¼ cup Parmesan, and thyme; season with salt and black pepper. Sprinkle crumbs evenly over gratin.
    cauliflower in a baking dish topped with breadcrumbs and shredded cheese
  7. Bake until crumbs are golden brown and sauce is bubbly, 25–30 minutes. Let gratin rest 10 minutes.


Notes

  • If you do not want to microwave the cauli, you can blanch it. Cook cauliflower in a pot of boiling salted water until crisp-tender, 2–3 minutes; drain.
  • This recipe is adapted from a recipe I originally developed for Cuisine at Home Magazine
  • The microwave time will largely depend on how powerful your microwave is. Check the tenderness of the cauliflower every minute or so to ensure it isn’t getting over-steamed.

Nutrition

  • Serving Size: ⅙ of the recipe
  • Calories: 230
  • Sugar: 7.5g
  • Sodium: 505mg
  • Fat: 13.5g
  • Saturated Fat: 9g
  • Carbohydrates: 17.5g
  • Fiber: 4.5g
  • Protein: 11.5g
  • Cholesterol: 39mg

Keywords: Cauliflower au gratin, Cauliflower gratin recipe

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About The Author

Lauren Grant is a professional culinary food scientist, food writer, recipe developer, and food photographer. Lauren is a previous magazine editor and test kitchen developer and has had work published in major national publications including Diabetic Living Magazine, Midwest Living Magazine, Cuisine at Home Magazine, EatingWell.com, AmericasTestKitchen.com, and more.

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