Creamy, cheesy, healthy, low-carb, and secretly easy to make – this Cauliflower au Gratin will put your other casserole recipes to shame! Cauliflower florets are roasted in the oven, tossed in a creamy Gruyere cheese sauce, topped with Parmesan cheese, and then baked until golden and crispy. You can serve this vegetarian and keto-friendly side dish for a fancy Thanksgiving or holiday dinner, or meal prep it for busy weeks!
Cauliflower au Gratin Recipe
To say this Cauliflower au Gratin is out-of-this-world delicious would be the understatement of the year.
Yes. I’m being 1000% real here.
Even my picky cauliflower recipe hubby went back for seconds and thirds of this low-carb casserole!
And it totally makes sense.
Cauliflower is cut into bite-sized florets, baked in the oven until tender, and then covered in a creamy, Gruyere cheese sauce that is to DIE for.
A mixture of Parmesan cheese and breadcrumbs are then sprinkled on top and broiled until golden and crispy.
The rich and savory sauce paired with the light and low-carb cauliflower will leave you satisfied but not overstuffed.
What Does “au Gratin” Mean?
“Au Gratin” is a French word that simply means “by grating.” Whether potatoes au gratin, or cauliflower au gratin (sometimes referred to as simply “Cauliflower Gratin”) normally means the dish is topped with grated cheese and/or breadcrumbs and then baked until browned.
The ingredients called for in this recipe are pretty similar to those found in a Scalloped Potatoes or potatoes au gratin recipe. The main difference being the use of low-carb cauliflower instead of starchy and carb-heavy potatoes.
- Cauliflower – You’ll need one large head, about 3 pounds, to give you roughly 5 cups of chopped florets.
- Flour – If you’re gluten-free, you can use a 1-to-1 blend.
- Milk – Cashew milk was used and tested in this recipe to reduce the amount of dairy used. Heavy cream or regular milk may also be substituted if you have that on hand. Almond milk is not recommended due to how thin it is. Coconut milk would also not work well since it has quite a strong flavor.
- Shredded Cheese – After testing and perfecting this recipe, the best shredded cheese to use is Gruyere. Shredded mozzarella, mild cheddar, or white cheddar will also work equally as well.
- Parmesan – A little bit of Parmesan cheese is mixed into the sauce as well as sprinkled on top to give the casserole a delightful crunch.
- Breadcrumbs – These give the topping a crunchy texture, but can either be left off or substituted with pork-rind crumbs if on a keto diet.
- Spices & Herbs – A hint of dried thyme and a bit of ground coriander are used to accent the cheeses selected. Feel free to get a little creative and try out dried rosemary and tarragon or a sprinkle of ground nutmeg, instead.
Preparing & Roasting Cauliflower
When cutting the cauliflower into florets, you’ll want to make them as close to the same size as possible.
Larger florets will give you a crunchier bite while smaller florets tend to overcook easily. So it’s best if you make your florets no smaller than about 1-inch in size.
If you look at other cauliflower gratin recipes, you will notice a variety of methods for pre-cooking the cauliflower.
Some call for boiling, others steaming, but the best way to do it is to roast cauliflower. (Much like in this Roasted Cauliflower recipe.)
Not only does baking bring out the natural and subtle sweetness of the cauliflower, but it also gives it a delightful crunch that boiling and steaming just can’t do.
Creamy Gruyere Cheese Sauce
If you have ever made a cream gravy from scratch, then you will know the basic process for making the creamy cheese sauce.
- You’ll first start by whisking together a bit of garlic, butter, and flour together in a skillet over medium heat. (step 1 & 2 above)
- After a few minutes a thick paste will form.
- This paste acts as the binder for the sauce so it is extremely important you whisk it over heat until it is nice and thick.
- Warmed or room temperature milk is then slowly added in, about ¼ cup at a time. (step 3 above)
- Much like when making risotto, you want to make sure the liquid is heated up so it does not bring down the temperature of the sauce.
- You can do this by either heating it in the microwave for 30 seconds or leaving it out at room temperature for 30 minutes before cooking.
- After each addition of milk, whisk the sauce until it is smooth and begins to thicken.
- Repeat this process over the course of 3-5 minutes.
- Once all of the milk is added, mix in the shredded cheese, seasonings, and half of the Parmesan cheese. (step 4 above)
- Stir until well combined.
How to Make
Once you have the cauliflower roasted, the Gruyere cheese sauce made, it’s just time to assemble it all together!
Pour sauce over baked cauliflower and toss to combine. (step 1 above)
Mix together remaining Parmesan cheese and breadcrumbs in a small bowl. Sprinkle over cauliflower. (step 2 above)
Reduce oven temperature to 400°F and return cauliflower dish to oven for 20-25 minutes. (step 3 above)
Tips to Make it Crispy
There are a few key things you can do to ensure you get a super crispy and not soggy topping on the au gratin:
- During the last 3-5 minutes of cooking, pop it under a high broil.
- Use a combination of breadcrumbs and Parmesan cheese in the topping.
- Do NOT cover it while baking! Covering it will trap in all of the excess moisture and make it soggy instead of crisp.
- Make sure to add JUST enough milk. Adding too much will make the sauce runny and not thick and creamy.
Since this cauliflower casserole would make an incredible Thanksgiving or Christmas side dish, here are a few pointers when it comes to prepping it ahead of time:
- Follow all of the recipe instructions but stop just before you sprinkle on the topping.
- Reserve the topping in a separate bowl and store in the refrigerator.
- On the day of serving, pull out the casserole at least 1 hour before baking to allow it to come to room temperature.
- Sprinkle topping over the cauliflower and follow the remaining steps for baking it in the oven.
Serving and Storing
If you’d like to impress your guests, add a few sprigs of fresh thyme and sprinkle some chopped thyme all over the casserole.
This cauliflower gratin tastes best when it is served immediately. You can save leftovers in the refrigerator for later, but they will get soggy and not have the same incredible texture.
If you would like to store leftovers, try and keep the casserole in its current dish. When ready to reheat, pull it out about 30 minutes ahead of time and then return to a 350°F oven for 10-20 minutes.
Cauliflower au Gratin Recipe
Allow me to introduce you to this cheesy Cauliflower au Gratin, your new favorite easy low-carb recipe! Serve this healthy vegetarian casserole for Thanksgiving or any holiday dinner.
- 1 large head cauliflower cut into florets, about 5 cups
- 2 Tbsp. oil olive or avocado
- 1 tsp. salt divided
- ¼ tsp. black pepper
- 2 Tbsp. butter or oil
- 2 cloves garlic crushed
- 2 Tbsp. flour gluten-free 1-to-1 blend
- 1 ½ cups milk regular or cashew milk
- ¾ cup cheese gruyere, asiago, or mixed
- ½ cup Parmesan cheese grated, divided
- ¼ tsp. dried thyme
- ¼ tsp. coriander
- ¼ cup Panko bread crumbs gluten-free, optional
Preheat oven to 425°F.
Add cauliflower florets to a 13 by 9-inch baking dish along with 2 tablespoons of oil, ½ teaspoon salt, and ¼ teaspoon black pepper.
Toss to combine and spread cauliflower out in the dish. Bake in preheated oven for 15-20 minutes.
While cauliflower is baking, add 2 tablespoons of butter and crushed garlic to a large skillet or saucepan. Saute over medium heat for 1 minute.
Sprinkle flour into the pan and whisk for 1-2 minutes, or until it begins to form a paste.
Reduce heat to medium-low. Pour in room-temperature milk, ¼ cup at a time, whisking well after each addition. Wait to add the next amount until the sauce has thickened.
Once all of the milk is added, turn off the heat and mix in gruyere cheese, ¼ cup Parmesan cheese, ½ teaspoon salt, thyme, and coriander.
Pour sauce over baked cauliflower and toss to combine.
Mix together remaining Parmesan cheese and breadcrumbs in a small bowl. Sprinkle over cauliflower.
Reduce oven temperature to 400 °F and return cauliflower dish to oven for 20-25 minutes.
For an extra crispy topping, broil casserole for 2-3 minutes under a high broil.
Serve with fresh thyme and enjoy!
- For a keto diet: Leave off the breadcrumbs and you'll bring the nutritional values to 156 calories, 7 carbs, and 2 grams fiber.
- Feel free to substitute the Gruyere cheese for a white cheese blend, Mozzarella, mild cheddar, or white cheddar.
- To Store: This cauliflower gratin tastes best when it is served immediately. You can save covered leftovers in the refrigerator for up to 3-5 days. Just note it will get soggy and not have the same incredible texture.
- To Freeze: Since the texture will change it is not recommended to freeze. If you do, seal it tightly in a freezer-safe airtight container for up to 3 months.