Bubbling with a creamy Gruyère sauce, cheesy Brussels sprouts au gratin is irresistible. A perfect dish to serve for Thanksgiving but don’t wait that long to try this delicious gratin.

Recipe Overview

Why you’ll love it: Everyone who tries this recipe raves about it! It’s so creamy and delicious.

How long it takes: 15 minutes to prep, 40 minutes to bake
Equipment you’ll need: 9 x 13 inch baking dish, saucepan
Servings: 8

Cheesy brussels sprouts gratin with a spoon scooping out one big cheesy scoop.
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I can’t believe we’re thinking about Thanksgiving already! It seems like we were just talking about inflatable rafts and sunscreen lotion.

Only take a look at the shelves in your grocery store though, and you’ll know that fall has arrived. All of the cool weather crops are displayed, inviting us to make the transition from summer eating (watermelons, cucumbers, corn on the cob, strawberries!) to autumn foods: winter squash, apples, pumpkins, cabbage, and Brussels sprouts. I love the flavors of fall, don’t you? 

I especially love these cheesy Brussels sprouts! Roasted lightly, then smothered with a creamy Gruyère cheese sauce, with a hint of nutmeg and thyme, and baked again until lightly browned and bubbling, these Brussels sprouts are a culinary delight!

Overhead view of a pan of brussels sprouts gratin.

About This Brussels Sprouts Gratin

Cheesy Brussels sprouts are a “gratin”. What does gratin mean? In French, “au gratin” means “by grating.” In traditional French cooking, a gratin is a made in a shallow dish containing potatoes, vegetables, or even seafood, covered with a lightly browned crust of  bread crumbs or cheese.

Au gratin can also mean casserole, or scraping from the pan, and I guarantee you’ll be scraping the pan of this Brussels sprouts gratin for every last delicious morsel.  

Seriously, when we were testing this recipe, we could hardly wait for this casserole to come out of the oven and we weren’t disappointed! Even people who are professed Brussels sprouts haters will be converted by the creaminess and flavor of this mouthwatering gratin. 

Brussels gratin in a white baking dish. Fresh thyme also pictured.

Brussels or Brussel

There is some confusion about how to spell the name of this tiny green cabbage-like vegetable. Many people use the spelling Brussel sprouts, omitting the “s” at the end of the word Brussels. Brussels sprouts are actually named for the Belgium city of Brussels so you definitely spell it with the “s” at the end. We don’t want to offend the good people of Brussels!

What You’ll Need

  • Brussels Sprouts: Look for fresh, firm dark green sprouts. You’ll need 2 bags, or about two pounds.
  • Olive Oil, Salt, Pepper: The Brussels sprouts are seasoned with salt and pepper and tossed with a bit of oil before roasting.
  • Onion: A yellow cooking onion is fine for this recipe; other types of onion work too.
  • Butter, Flour, Whole Milk: This trio makes up the simple white sauce which is the base of the gratin.
  • Thyme: Use fresh if you can but dried is fine, too. Use less if you’re using dried thyme because it’s more potent than fresh.
  • Nutmeg: Freshly grated nutmeg is so much better tasting than ground nutmeg! Look for whole nutmeg and use a fine grater.
  • Gruyère cheese: This hard cheese is a type of Swiss cheese. It is more dense and doesn’t have large holes like typical Swiss cheese. It melts easily and has a sharper flavor.

How To Prep Brussels Sprouts

Prepping and pruning those tiny green cabbages can seem tricky the first time you do it.

  • Look for firm, compact, dark green Brussels sprouts that don’t have worm holes, aren’t shriveled, or have yellowing loose leaves.
  • Rinse them well in a colander under running water.
  • Using a sharp paring knife, cut off the tough stem, about even with the edge of the sprout.
  • Peel away discolored or wilted outer leaves.
  • For this recipe, cut the sprouts in half lengthwise. Whether or not you cut your sprouts depends on their size. You want them to be uniformly bite-sized. Just remember: Halving the sprouts allows the cheesy sauce to permeate each tasty morsel!
  • If you’d like a visual of how to prep Brussels sprouts, take a look at this informative YouTube video
Close up view of Brussels sprouts and cheese in a white baking dish.

How To Make Cheesy Brussels Srouts

Prep all of the ingredients. You’ll want to have all the ingredients for making this recipe prepared before you begin cooking it. Prep the Brussels sprouts, grate the Gruyère, measure the milk, flour, and butter for the white sauce, grate the nutmeg, and chop the thyme.

Preheat the oven and choose a dish. Get your oven preheating to 400ºF and prepare your baking dish. You’ll want to use a nice looking shallow glass dish for this recipe because you’ll be serving the gratin right from the dish. 

Roast the Brussels sprouts. Toss the prepped Brussels sprouts with a bit of olive oil, season with salt and pepper, spread them in the baking dish, and roast for about 20 minutes, or until they’re just beginning to brown slightly.

Make the cheese sauce. Meanwhile, prepare the white sauce on the stovetop, whisking in the cheese, nutmeg, and herbs when the sauce has thickened.

Bake. Pour this creamy cheese sauce over the sprouts (you might want to reserve a spoonful or two for tasting because it’s soooo good), sprinkle the top with additional grated Gruyère, and pop the dish back into the oven for 20 minutes or so, until it’s brown and bubbling.

Cool before serving. Let the casserole cool for 5 to 10 minutes before serving. Serve it right from the baking dish. 

FAQs

How can I improve the taste of Brussels sprouts?

If you have only tried boiled overcooked Brussels sprouts, you may think they taste bad or have a strong flavor. I would encourage you to try some of the newer recipes that are popular.
Brussels sprouts salads are much like coleslaw. We love this salad with grapes and Parmesan or Brussels sprouts salad with apples, cranberries, and walnuts.
Roasted Brussels sprouts have become very common in restaurants and once you’ve tried them, you’ll understand why. Try roasted Brussels sprouts with maple & cayenne!

Cheesy brussels gratin being scooped out a white baking dish.

Make It Your Own

  • Try a different cheese. The slightly nutty flavor of Gruyère really is perfect in this gratin but other types of cheese can be substituted: Swiss cheese, sharp cheddar, Parmesan or Asiago.
  • Add bacon or pancetta. Just cut it into 1 inch pieces, cook until done, drain, and add it with the cheese. 
  • Experiment with the spices and herbs. If you love garlic, try adding a bit of garlic powder to the white sauce. Paprika is a good addition, as well, maybe sprinkled on the top to add a little color. If you’re not a nutmeg fan, leave it out. It will still taste great!
  • Lighten it up by using low fat milk to make the white sauce. It won’t be quite as creamy but you’ll save some calories and fat. If you’re really looking to cut calories, don’t mix any cheese into the white sauce and just sprinkle a half cup on top of the gratin before baking. 
  • Not a fan of Brussels sprouts? Try scalloped sweet potatoes with bacon and Gruyère instead. Asparagus casserole is pretty amazing, too.

More Brussels Sprouts

If you’re looking for everyday options, try grilled Brussels sprouts, air fryer Brussels sprouts, or sautéed Brussels sprouts.

Make-Ahead Ideas

Get a head start: Prep the Brussels sprouts up to two days ahead. The onions can be chopped ahead too. Store separately in covered bowls or resealable bags in the refrigerator. Shred the cheese and store in the refrigerator for up to a week.

Storage & Reheating Tips

This dish is really best eaten right away. If you do have leftovers, heat them gently in the oven until they’re heated through, or in the microwave. The gratin will keep a couple of days in the fridge. 

Special Occasion Side Dishes

Recipe

Cheesy Brussels Sprouts au Gratin

4.50 from 4 votes
Prep: 15 minutes
Cook: 40 minutes
Total: 1 hour 5 minutes
Servings: 8 servings
Bubbling with a creamy Gruyère sauce, cheesy Brussels sprouts au gratin is irresistible. A perfect dish to serve for Thanksgiving but don't wait that long to try this delicious gratin.
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Ingredients 

  • 2 pounds Brussels sprouts
  • 1 tablespoon olive oil
  • ¼ teaspoon kosher salt
  • teaspoon ground black pepper
  • 2 tablespoons unsalted butter
  • ½ cup diced yellow onion (about ½ medium onion)
  • 2 tablespoons all-purpose flour
  • 1 ¾ cups whole milk
  • 1 teaspoon roughly chopped fresh thyme (or ½ teaspoon dried thyme)
  • ¼ teaspoon freshly grated nutmeg
  • 4 ounces Gruyère cheese, shredded and divided

Instructions 

  • To prepare Brussels sprouts, rinse well. Trim off bottom (stem) end and remove any brown or tough outer leaves. Cut in half from top to bottom.
  • Preheat oven to 400ºF. Spray a 9 x 13-inch baking dish with nonstick baking spray. 
  • Mix Brussels sprouts with olive oil, salt, and pepper, and add to prepared baking dish.
  • Bake for 20 minutes or until starting to brown. Remove from oven.
  • While Brussels sprouts are roasting, in a medium saucepan over medium heat, melt butter. Add onions and sauté, stirring constantly, until translucent, or about 2 minutes. 
  • Add flour and continue to stir or whisk for 1 minute.
  • Slowly add the milk, stirring constantly, and cook over medium-low heat until thickened, 10 to 12 minutes. Remove from heat.
  • Add thyme and nutmeg to the sauce, and stir to combine. Stir in half of the cheese until melted. Pour cheese sauce over Brussels sprouts, stirring lightly to combine. Top with remaining cheese. 
  • Bake for 20 minutes, or until top is starting to brown and gratin is bubbling. 
  • Let cool 5 to 10 minutes before serving.

Notes

  • If desired, add bacon or pancetta to the gratin. Cook diced bacon or pancetta until crisp, drain well, and stir into the sauce with the thyme and nutmeg.
  • Other types of cheese can be substituted. Try Swiss cheese, sharp cheddar, Parmesan or Asiago.
  • Make ahead tip: Prep Brussels sprouts and onion and store in separate containers in the refrigerator up to two days in advance. Shred cheese up to a week in advance.

Nutrition

Calories: 192kcal, Carbohydrates: 15g, Protein: 10g, Fat: 11g, Saturated Fat: 6g, Polyunsaturated Fat: 1g, Monounsaturated Fat: 4g, Trans Fat: 1g, Cholesterol: 28mg, Sodium: 172mg, Potassium: 543mg, Fiber: 5g, Sugar: 6g, Vitamin A: 1176IU, Vitamin C: 98mg, Calcium: 256mg, Iron: 2mg

Nutrition information is automatically calculated, so should only be used as an approximation.

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4.50 from 4 votes (4 ratings without comment)

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2 Comments

  1. denise says:

    looks decadent

    1. Rachel Gurk says:

      Definitely is!