Make way for creamy, cheesy goodness. Cauliflower Au Gratin is the cold-weather comfort food you need to get through the holiday season. With simple, whole ingredients, this easy au gratin cauliflower recipe guarantees you still get your veggies in when all you’re craving is mac and cheese.
If you’ve spent any significant time on this site, you’ll know we have diverse palates ’round here. We don’t shy away from seasoning, heat, or interesting flavors. And we certainly don’t shy away from health-ifying comfort foods.
But deep in my heart, I am basic as hell when it comes to casserole.
If I see a baking dish come out of the oven with cheese bubbling up like molten lava through a bed of crunchy, golden brown breadcrumbs, I’ve got on a bib and am at the table with a fork and bowl before it’s had time to cool enough to be edible.
This baked cauliflower gratin has both those things, but it also has cauliflower. (So, you know, fiber, vitamins, minerals… all the other good stuff.) It’s creamy, cheesy, and wholly satisfying for those of us that spend our waking hours secretly craving homemade baked mac and cheese.
Cauliflower au gratin is a simple, homestyle casserole with a fancy-pants name (heck, go whole-hog and call it choufleur au gratin) that you can serve on the most basic or special of occasions. Plus, it frees your up your spuds for other delicious recipes besides potatoes au gratin.
For a condensed post with just the need to know facts, click to view the web story for this cheesy cauliflower casserole!
How to Make Cauliflower au Gratin
Crowd-pleasing Cauliflower Au Gratin is an easy, cheesy side that’s the perfect combination of healthy veggies and homey comfort. Make the cheese sauce in advance or use frozen florets to save yourself prep time.
Part 1: Make the Cheesy Sauce
- SAUTE. Heat butter in sauce pot over medium high heat until it melts, then foams. Add the onion and cook until softened, then add the garlic and cook until fragrant.
- THICKEN. Sprinkle flour over the onions and garlic. Work it in with a rubber spatula until thickened and paste-like (this is called a roux).
- ADD MILK. Gradually pour in the milk, whisking constantly to avoid clumping (it is now a bechamel sauce).
- SIMMER. Simmer until the bechamel is thick and easily coats and clings to your spatula.
- CHEESE PLEASE! Season with salt, pepper and nutmeg, then the add cheese in small batches. Whisk after each addition until very smooth.
Note: Cheese sauce can be made up to 24 hours in advance. Reheat over low heat on the stove to warm through. Whisk until smooth.
Part 2: Make the Cauliflower Au Gratin Casserole
- PREP. Preheat the oven to 375°F. Lightly mist a 2-quart (small) casserole dish with cooking spray or a bit of melted butter.
- STEAM. Steam the cauliflower, then transfer to the casserole dish and arrange in a single layer.
- Reheat the sauce if you made in advance.
- SAUCE IT. Pour the cheesy sauce over the florets, then gently combine.
- TOP IT. Combine the melted butter and breadcrumbs, then sprinkle over the casserole dish.
- BAKE. Bake uncovered for 25-30 minutes, until bubbling and golden brown.
- SERVE. Garnish with parsley and serve.
Note: Cauliflower can be steamed on the stove top, in the Instant Pot, or even in the microwave!
- Make sure to add cheese to the roux in small batches. Getting out big clumps takes more time when you dump it in at once, and you may end up overcooking the sauce in the process.
- Steam cauliflower florets just tender, not soft. You want them a little firm since they’ll continue to cook when you bake the cauliflower au gratin.
- Use any preferred neutral oil (or cooking spray) to grease the dish, but don’t shy away from doing it with even more butter. Yum!
What Kind of Cheese Should I Use?
We love the tangy combination of gruyere and cheddar in this cauliflower au gratin recipe, but you can use any “melty” cheese combo you like.
Can I use Frozen Cauliflower?
Absolutely! Since it’s getting steamed, then baked, frozen cauliflower florets are a great way to make your prep easier and save time. Follow the package directions for steaming, but undercook by 1 minute to ensure the florets aren’t too soft.
More Holiday-Worthy Cauliflower Sides
- Cauliflower Mashed Potatoes
- Roasted Cauliflower Soup
- Creamy Cauliflower Risotto
- Loaded Cauliflower Soup
- Oven Roasted Cauliflower
Did you make this cauliflower au gratin? I’d love to know how it turned out! Leave a comment and a rating below.
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- 2-quart Saucepan
- 2 Quart Casserole Dish
- Rubber Spatula
- 2 medium heads cauliflower, divided into florets, about 12 cups
- 4 tbsp butter
- 1 medium yellow or sweet onion, diced
- 2 cloves garlic, minced
- 4 tbsp all purpose flour
- 2 c whole milk
- 1 tsp kosher salt
- ½ tsp ground pepper
- ¼ tsp nutmeg, freshly grated, if available
- 2 c cheese, gruyere and cheddar
- ½ c panko breadcrumbs
- 1 tbsp melted butter
- Heat the oven to 375°F. Lightly mist a 2-quart casserole dish with cooking spray, or grease with a pat of butter.
- Steam cauliflower the cauliflower using your preferred method until the florets are crisp-tender, but not soft. See notes.
- Heat a 2-quart saucepan over medium heat. Add the butter and heat until it melts, then foams. Add the onion and cook until softened and translucent, 5-6 minutes, stirring occasionally. Add the garlic and cook 1 minute more, or until fragrant, stirring constantly.
- Sprinkle the flour over the onion and garlic mixture. Work in with a rubber spatula until it forms a paste-like consistency.
- Gradually pour in the milk, whisking constantly to avoid clumping. Bring to a steady simmer and cook until the sauce is slightly thickened and easily coats the spatula, about 5 minutes.
- Whisk in the salt, pepper and nutmeg. Reduce the heat to low, then add the cheeses in small batches (about ½ cup), whisking after each addition until very smooth.
- Arrange the steamed cauliflower in the prepared casserole dish. Pour the sauce over the florets, then gently toss evenly coat the florets.
- Combine the breadcrumbs and butter in a small bowl and stir until the breadcrumbs are evenly moistened. Sprinkle the mixture evenly over the casserole dish.
- Bake uncovered 25-30 minutes, until bubbling and golden brown.
- Rest five minutes, then garnish with parsley and freshly grated nutmeg (if available). Serve hot or warm.
Steamed Cauliflower MethodsInstant Pot
- Pour ½ cup water into the inner pot. Position a trivet or all metal steamer basket in the pot. Place the florets into the steamer basket, then sprinkle with ½ tsp kosher salt.
- Secure the lid and ensure the pressure valve is set to Sealing. Program to HIGH pressure 3 minutes for crisp tender florets. It will take approximately 10 minutes for the pot to come to pressure.
Once the timer goes off, press the Cancel button to turn off the Instant Pot. Then perform a manual pressure release by turning the venting knob from Sealing to Venting. Once the float valve has dropped, open the lid away from your body to allow the steam to escape. Carefully remove the steamer basket with oven mitts, or remove the florets with a slotted spoon.
- Place the florets into a microwave safe bowl, then sprinkle with ½ tsp salt. Add the water, then cover the bowl with a plate.
Microwave 5 minutes for crisp tender florets. Strain the cauliflower from the steaming water.
- Fill a pot large enough to accommodate a steamer basket with 1.5-2” water. Position the steamer basket in the pot, then bring the water to a simmer over high heat.
- Place the florets into the steamer basket, then sprinkle with ½ tsp kosher salt. Reduce the heat to medium low to maintain a steady simmer, then cover.
Steam 5-6 minutes for crisp tender florets. Remove the steamer basket from the pot.