Roasted Cauliflower Gratin

Rich and decadent cauliflower gratin is a great side dish for holiday dinners. Roasted cauliflower is combined with a cheddar cheese sauce flavored with onion and garlic. Make it for Easter, Thanksgiving, Christmas, or other special occasions.

A holiday table or other celebration meal is not complete without a gratin, which is just a dish – in this case, roasted cauliflower – that is baked with a sauce and cheese or breadcrumbs on top.

And so for this roasted cauliflower gratin, we start with a classic bechamel sauce that, up until now, I thought was just a simple combination of milk, flour, and butter.

Homemade Béchamel Sauce

When I set out to learn about the five mother sauces, I was excited about all of them except one – bechamel. What’s to get excited about? I’ve made it a thousand times (mac & cheese is a lifelong love), so my initial thought was  “how boring.”

My plan was to sort of slip it in on my way to more exciting parts of this series (bring on the classic tomate and espagnole sauces!). However, despite my dead-beat approach to making bechamel, I did do my research and – lo and behold – I learned some things! And I used the bechamel sauce to make a rich and comforting roasted cauliflower gratin.

Notes About the Sauce

So, I was surprised to learn that a lot of bechamel recipes call for an onion that you simmer in the butter, flour, milk mixture. 

I’ve never done that before and you might think it makes it all onion-y weird, but it doesn’t and the sauce ends up with just a subtle hint of onion.

Many classic recipes also call for one whole clove that you stick in the onion. I’ve done it with and without the clove and I honestly can’t tell the difference. So my bechamel is sans clove.

Ingredients

• Unsalted butter
• All-purpose flour
• Whole milk
• Onion wedge
• Cauliflower florets
• Whole head of garlic
• Olive oil
• Shredded cheddar cheese
• Salt and pepper

I learned I’ve been making bechamel wrong my whole life. Or I should say, I’ve been way too loosey- goosey with my bechamel up until now. I never paid much attention to the ratio of butter/flour/milk preferring to instead fly to by the seat of my pants.

I also learned you have to take your time (I’ve always rushed through the process before) and, by the way, that time investment is so worth it – the resulting sauce was so creamy and had the most amazing consistency. Like, “Can I just drink that straight from the saucepan” amazing.

How to Make Cauliflower Gratin

For this gratin, we are roasting cauliflower florets and garlic until they are caramelized and delicious. Roast them at 425°F for about 30 minutes.

While the cauliflower and garlic are roasting, you can make the cheese sauce, starting with a classic bechamel.

First, melt the butter in a saucepan. You want the sauce very white (hence its nickname ‘white sauce’), so melt the butter over pretty low heat before adding the flour to make the roux (a lesson I learned after making veloute sauce).

Next, you add milk and whisk until you have a smooth, white sauce. Add the onion wedge and cook the sauce until it’s thick enough to coat the back of the spoon.

Once the sauce is thickened, discard the onion. Squeeze the cloves out of the roasted garlic and mash them up. Add them to the sauce and stir.

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To turn it into a cheese sauce, all you do is add… yes, cheese. Cheddar cheese. Add it and stir until it’s melted into the sauce.

Add the roasted cauliflower florets to the sauce and then pour it all into a baking dish.

Sprinkle more cheese over the top and place the baking dish under the broiler until the cheese is melted and the gratin is bubbling hot.

This recipe easily stretches to serve six if it’s served with other side dishes. It’s very rich and decadent so a little goes a long way. That said, you can easily double it if you want bigger servings or to serve more people.

It’s definitely what I consider “celebration food” – you know, a dish that is perfect for a holiday dinner like Easter or Thanksgiving. It’s a great side dish for ham or turkey.

Happy cooking,

More Decadent Side Dishes

• Brussels Sprouts Gratin
• Mushroom Macaroni and Cheese
• Creamy Potato Casserole with Leeks
• Crock Pot Mashed Potatoes

📣 Do you love this recipe? I would love to know! Leave a comment below the recipe along with your recipe star rating.

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The nutrition information in this recipe is an estimate only and was calculated using Nutrifox, an online nutrition calculator.

Post, photos, and recipe were updated in March 2021.