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Add a little kick to dinner when you make this easy, cheesy Horseradish Cheddar Mashed Cauliflower Casserole. This light and healthy vegetable side dish can be prepared ahead for a busy weeknight or even a holiday meal. Everyone will love this keto-friendly and gluten free casserole.
Want yours fully loaded? Try Bacon Cheddar Cauliflower Mashed Potatoes!
Horseradish Cheddar Mashed Cauliflower Casserole – Easy, Cheesy Side Dish!
I think I was fed way too many mashed potatoes as a kid because unless they have all kinds of stuff added to them, like Bacon Cheddar Cheesy Mashed Potatoes, I’ll usually pass them right by. But give me a serving or three of mashed cauliflower all day, any day.
Especially this cauliflower casserole. It’s nice and fluffy because adding Greek yogurt and an egg and then baking it in the oven gives it a fluffy consistency and some structure. It’s not just a runny cauliflower puree. Then it’s kicked up with sharp and slightly spicy horseradish cheddar cheese.
Now, I’m not going to try to tell you that cauliflower gratin tastes like mashed potatoes. Nobody buys that lie anymore. But this simple low carb side dish is simple to make and tastes amazing. It’s easy enough for a weeknight dinner, but special enough for a holiday meal.
You only need four ingredients plus your basic seasonings. Just gather these together, then scroll to the recipe card for the full amounts.
- Cauliflower: you’ll need the florets from one head. No need to cut them to any particular size since you’ll be steaming and pureeing them
- Egg: Just one helps to bind it together and give it a thicker and fluffier texture than just plain mashed cauliflower.
- Plain Greek yogurt: Gives it a creamier texture while still keeping it light and fluffy without thinning it out.
- Horseradish Cheddar Cheese: I used Cabot Horseradish Cheddar. Don’t want the spice. Plain cheddar cheese works just fine!
- Seasonings: Just your basic salt and pepper, with some optional paprika on top to give it a little color.
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 in the recipe card.
Steam the cauliflower. Place the cauliflower in a steamer basket over a pot of water and steam until it is very tender.
Make the mash. Transfer the steamed cauliflower to a blender or food processor. Add the egg, yogurt, cheese, salt, and pepper. Pulse and puree until it is smooth.
Transfer to baking dish. Add the mashed cauliflower to a casserole dish and spread it to make it smooth on top. Top with more shredded horseradish cheddar cheese and some paprika, if you like, for color and a hint of smokiness.
Bake and serve. Baked the cauliflower casserole at 400°F for 25 to 20 minutes until it is hot and golden-brown on top. Baking it gives it that fluffy texture just like mashed potatoes.
Tips for Success
- Get rid of excess moisture. After you steam the cauliflower, take it out of the pot so some of the steam can evaporate and get rid of some of the liquid on the cauliflower.
- Choose your consistency. 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.
- Make it fancy. If you are having a dinner party, you can put it into individual ramekins, as I did with this Whipped Cauliflower Gratin. Just adjust your baking time a bit.
Can you make cauliflower casserole in advance?
One great thing about this easy mashed cauliflower casserole recipe is that you can prepare all or part of it in advance. This makes it ideal for busy weeknights OR holiday meals, where you have to prepare a lot of dishes. Here are your options.
- Pre-cook the cauliflower. Steam the cauliflower, then let it cool down and dry off. Then you just have to puree and bake when it’s time to serve.
- Prepare but don’t bake. Get the entire mashed cauliflower casserole prepared and refrigerate it unbaked. You’ll want to take it out of the refrigerator to warm up a bit or give it a little extra time in the oven to get hot all the way through.
- Bake and reheat. Bake it off completely then reheat it in the oven to get the cheese extra toasty.
Storing and Reheating Leftovers
Whether you’ve made the cauliflower casserole in advance or just have leftovers, you can wrap it or cover it tightly and refrigerate it for 3 or 4 days. Freezing and thawing it would likely give it a watery consistency.
Then you can reheat it by microwaving all or a portion of it, or put it back in the oven at 350°F to 400°F for about 20 minutes until it is hot all the way through.
I make this veggie side dish with so many meals. It’s so quick that I can make it for weeknights, but the flavor is a perfect match for many holiday meals.
- Busy weeknight. Have it with your favorite low carb dinner recipe, like Pan-Seared Cube Steaks Without Flour.
- Weekend dinner. It’s nice to pair with an Air Fryer Rotisserie Chicken or Bottom Round Roast.
- St. Patrick’s Day. You’ll love how it tastes with Easy Slow Cooker Corned Beef and some Peas and Carrots.
- Easter and Passover. The creamy little kick of horseradish tastes amazing with ham or brisket.
- Christmas. You can’t go wrong serving it with Cranberry Crusted Prime Rib.
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 Mashed Cauliflower Casserole
- 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.