Horseradish Cheddar Cheesy Mashed Cauliflower Gratin

5 from 2 votes
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Cheesy Mashed Cauliflower Gratin is a fluffy side dish kicked up with Horseradish Cheddar Cheese. This light and healthy vegetable side dish can be prepared ahead for a busy weeknight and is a delicious veggie for a holiday meal or an elegant dinner. Everyone will love this keto-friendly whipped cauliflower casserole. In fact, it’s one of the best gluten free casserole recipes.

Horseradish Cheddar Mashed Cauliflower Casserole

Horseradish Cheddar Mashed Cauliflower Gratin


I think The Hubby and I were clearly fed way too many mashed potatoes when we were kids because now we just don’t like them. Occasionally I’ll make some sort of smashed potatoes that are jazzed up with something flavorful and left kinda chunky – like this Balsamic Caramelized Onion Mashed Potatoes or Bacon Cheddar Cheesy Mashed Potatoes, and that is fine.

But plain, smooth, creamy mashed potatoes never happen in our house. So when a pile of white stuff shows up on The Bug’s plate, even he knows it’s cauliflower. And he is cool with that.

I love my kid as much as he loves the mashed cauliflower.

This simple low carb side dish is simple to make and tastes amazing. Simple mashed cauliflower is kicked up with horseradish cheddar cheese and baked in a casserole to give it a light and fluffy texture and amazing flavor. It’s easy enough for a weeknight dinner, but special enough for a holiday meal. 

Now, I’m not gonna try to tell you that cauliflower gratin tastes like mashed potatoes. Nobody buys that lie anymore. But I like cauliflower and my family likes cauliflower. So when I say that we are having cauliflower with dinner, I don’t get any complaints. If you want to try to fool your kids, that’s on you. 🙂

gluten free Cauliflower Gratin with Horseradish Cheddar CheeseLow Carb Mashed Cauliflower Casserole


You only need four ingredients plus a little salt and pepper for flavor and some optional paprika for a little color on top. Just gather these together.

  • Cauliflower: you’ll need the florets from one head. No need to cut them any particular size since you’ll be steaming and pureeing them
  • Egg: Just one helps to bind it together and give it a thicken and fluffier texture than just plain mashed cauliflower.
  • Plain Greek yogurt: Gives it a creamier texture while still keeping it light and fluffy and not too thin.
  • Horseradish Cheddar Cheese: I used Cabot Horseradish Cheddar. Don’t want the spice. Plain cheddar cheese works just fine!
A head if cauliflower, an egg, and bowls with horseradish cheddar cheese, Greek yogurt, salt, pepper, and paprika on a marble tabletop

How to Make Cauliflower Gratin with Horseradish Cheddar

Just a quick overview here and some process photos to help you out. You’ll find all the details and the full quantities of ingredients in the recipe card.

  1. Start by steaming the cauliflower until it is very tender.
  2. Puree it with egg, Horseradish Cheddar Cheese, Greek yogurt, salt, and pepper.
  3. Spread it into a baking dish and top with shredded cheddar cheese (and the optional paprika, for color, if you like).
  4. Pop it in the oven to give it that fluffy texture just like mashed potatoes.

Tips for Success

  • If you are having a fancy little dinner party, you can put it into individual ramekins, as I did with this Whipped Cauliflower Gratin. Just adjust your baking time a bit.
  • Also, it never hurts to add bacon, like this Cheesy Cauliflower Mashed Potatoes recipe.
  • If you puree it in a high-powered blender, you will get a smooth and silky whipped cauliflower. A food processor makes them more like a thicker cauliflower mashed potatoes recipe.

Is cauliflower gratin gluten-free?

A traditional gratin (or the extra fancy term, au gratin) is a dish with a baked topping of bread crumbs and cheese. To make this a gluten-free gratin, the bread crumbs are left out. But trust me; this cheesy mashed cauliflower casserole is equally delicious without them.

Nice and fluffy, but because you add Greek yogurt and egg, and then bake it, there is structure to it. It’s not super creamy (though it is smooth), and if you let the cauliflower drain well, it won’t be watery either. Then you get the sharp cheddar cheesiness and the little kick of horseradish, which totally isn’t overwhelming. Evidence – I had an almost four-year-old and a one-year-old shoveling this in their mouths.

Can you make gratin ahead of time?

One great thing about this easy gratin recipe is that you can prepare all of part of it in advance, which makes it ideal for busy weeknights OR holiday meals, where you have to prepare a lot of dishes.

To make the cauliflower gratin ahead:

  • Steam the cauliflower, then let it cool down and dry off (that actually keeps it from being too watery).
  • OR, get the entire mashed cauliflower casserole prepared and refrigerate it unbaked, or bake it off completely then reheat it in the oven to get the cheese extra toasty. (That’s what I did since I was taking photos at around 3 in the afternoon).
A scoop of Horseradish Cheesy Mashed Cauliflower in a small bowl

What do you serve with Cauliflower Gratin with Horseradish Cheddar Cheese?

Make it a Meal
A scoop of Horseradish Cheddar Mashed Cauliflower Casserole
Brianne’s Favorite Blender

I love to use my Blendtec. It is a high-powered blender that gives you the smoothies and creamiest mashed cauliflower, smoothies, soups, and more.

I am a Blendtec ambassador, and should you make any purchases through my  Blendtec Store link, I will receive a small commission, but that also means you can use the code CUPCAKESANDKALECHIPS to receive 20% off.

Horseradish Cheddar Whipped Cauliflower
5 from 2 votes

Cauliflower Gratin with Horseradish Cheddar Cheese

Fluffy and cheesy with a little kick, Horseradish Cheddar Cauliflower Gratin is a light, healthy vegetable side dish for a busy weeknight or a holiday meal. A gluten-free and low carb side dish!
Prep: 10 mins
Cook: 40 mins



  • Preheat your oven to 400°F, and lightly coat a 2 quart casserole dish with oil or cooking spray.
  • Cut the cauliflower into large florets, discarding the tough stem, and steam over boiling water until very tender.
  • Drain thoroughly, and allow to cool slightly so that some of the excess moisture evaporates.
  • Place the cauliflower, Greek yogurt, egg, 3/4 cups of the cheese, salt, and pepper into a blender or food processor, and process until smooth.
  • Transfer the cauliflower to the prepared dish and sprinkle with remaining cheese, and paprika, if desired.
  • Bake for 25-30 minutes, or until heated through and browned on top.


You can also divide the cauliflower mixture between 4-6 ramekins and bake for 15-20 minutes.
The casserole can be prepared ahead of time and baked or reheated before serving.
Nutrition Facts
Cauliflower Gratin with Horseradish Cheddar Cheese
Amount Per Serving (1 g)
Calories 117 Calories from Fat 63
% Daily Value*
Fat 7g11%
Saturated Fat 4g20%
Cholesterol 47mg16%
Sodium 547mg23%
Potassium 315mg9%
Carbohydrates 5g2%
Fiber 1g4%
Sugar 2g2%
Protein 8g16%
Vitamin A 230IU5%
Vitamin C 46.2mg56%
Calcium 172mg17%
Iron 0.7mg4%
* Percent Daily Values are based on a 2000 calorie diet.


More vegetable side dishes

  1. Melody

    I dont think i have ever seen horseradish cheddar at our local supermarket. If i cant find it how much horseradish would i mix with cheddar cheese to get the same taste?

  2. Ginger

    This tastes great! I used Cabot Cheddar and added some miscellaneous hot mustard sauce. I also bought a purple caluiflower head. I hope the kids will enjoy it as much as I just did! 😀

  3. Sally

    Id luv to try this…only prob is that although we are lucky enough to live in land of cheese (and cuckoo clocks) alas we cannot buy anything more than a fairly mild non descript cheddar here…
    Any ideas on how I could replicate your flavours without your horse radish cheddar?
    am hoping to make this tomorrow for dinner so would be very grateful if have time x quick tip…otherwise it’ll be my much loved bit pretty uninspiring cauliflower and cheese

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  5. I am cooking dinner for friends tomorrow night and was looking for side ideas, Brianne, so this has come at the perfect time. I have both cauliflower and broccoli so I’m going to mix them for this beautiful dish. Thank you!

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