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Ultra-creamy and cheesy – this Brussels Sprouts au Gratin requires just 8 ingredients (plus a few pantry staples) and 15 minutes of hands-on preparation! Featuring roasted brussels sprouts and pearl onions smothered in a decadent, creamy gruyere cheese sauce, and topped with a buttery, crunchy topping! These restaurant-worthy gratin brussel sprouts are the perfect delicious and easy side dish for any occasion. One bite and these cheesy sprouts will become a family favorite!

Featured comment: Outrageously delicious! Thank you for sharing this recipe!” – Suzanna

Overhead photo of brussels sprouts au gratin in an oval baking dish with two serving spoons inserted into the casserole.

Update: This post was originally published in November 2014. I made updates to the post below to include new photos and more information about brussels sprout gratin. Plus, there’s now comprehensive step-by-step photos, plus a recipe video showing you JUST how easy this gratin recipe is to prepare! 

Hi friends! Are you ready for the creamiest, dreamiest, most swoon-worthy side?

Today’s recipe just so happens to be my all time favorite vegetable side dish, especially for the holidays! And, after you give it a taste, I’m confident you and your family will love it too!

Table of Contents

About this brussels sprouts gratin recipe

This recipe for au gratin brussels features a combination of roasted tender-crisp brussels sprouts and sweet pearl onions smothered with a creamy, rich cheese sauce. Sprinkled with a crunchy, buttery topping and baked until golden brown and bubbly around the edges, this vegetable side dish is so delicious even the brussels sprouts haters will ask for seconds (or thirds)!

Listen up, especially if you think you don’t like sprouts! The brussels sprouts in this gratin are NOTHING like the memories you hold of your grandmother’s or mother’s sprouts (no offense to them). You know those over-cooked, mushy, sad and lifeless sprouts. These gratin brussels sprouts are everything a vegetable should be – they’re perfectly tender-crisp, flavorful and highly delicious!!

I pinkie promise you will love these sensational sprouts! If you plan on having a veggie hater at your holiday table, or perhaps you, yourself, are the sprout hater, well then, you simply must try this gratin recipe! Fair warning though, prepare to be totally blown away in the very best way. There is a very good chance this dish will even transform you into a brussels sprouts addict for life!

Why these gratin brussel sprouts works

  • So much flavor! Infusing the cream sauce with aromatics adds extra flavor, while the cheese and seasonings do their traditional thing.
  • Perfectly tender-crisp sprouts! Partially roasting the brussels sprouts before assembling the gratin ensures they are *chef’s kiss* tender-crisp.
  • Ultra rich and creamy gratin sauce! Baking the brussels au gratin uncovered allows the cream sauce to continue thickening and beautifully coat the vegetables.
  • Chef tested and approved! This recipe is tried, true and easy to follow. Plus, it tastes pretty perfect, too!

Photo of chopped fresh brussels sprouts on a wood cutting board.

What is brussels sprouts au gratin?

Brussels sprouts au gratin is an indulgent cheese baked dish, similar to a casserole. Au gratin brussels features trimmed brussels sprouts (along with onions and garlic) cooked in sauce of cheese with breadcrumb topping. The casserole is then baked in the oven until golden brown and bubbly.

What does au gratin mean in english?

Gratin, or au gratin, is a cooking technique in which a dish is sprinkled with breadcrumbs and/or cheese, and then baked or broiled until the topping is golden brown.

The phrase “au gratin” derives from the French word gratter which means “to grate”. However, in the culinary world “au gratin” refers to any dish with a browned topping, usually cheese and/or breadcrumbs. Popular au gratin dishes include potatoes au gratin and spinach au gratin.

How to pronounce au gratin?

You can pronounce au gratin as oh-gra-tan or aw-graht-n.

Ingredients for brussels sprout gratin

This easy brussels sprout side dish is rich and bursting with flavor! This cheesy sprout recipe only requires 8 ingredients, plus a few pantry staples, to create a dish that is insanely delicious!

  • Brussels Sprouts: You need 1 pound of brussels sprouts. Look for ones that are bright green in color and firm to the touch. Their leaves should be tightly packed. I recommend selecting small to medium size brussels sprouts as they are sweeter and more tender than the larger ones.
  • Pearl Onions: While frozen pearl onions aren’t the most attractive vegetable, they are incredibly convenient! Make sure you fully thaw and thoroughly pat them dry. You can absolutely use fresh onions if desired – just make sure you trim, blanch and peel them before proceeding with the recipe.
  • Butter: Use unsalted butter so you can control the saltiness of the dish!
  • Garlic: One clove of fresh garlic adds a distinctive, punchy taste.
  • Thyme: Fresh thyme infuses the sauce with a subtle earthy flavor.
  • Flour: Two tablespoons of all-purpose flour help thicken the creamy sauce.
  • Cream: Two cups of heavy cream creates the base for a luxurious, rich sauce. While you may be tempted to cut calories and use half & half or milk, don’t!
  • Seasonings: Ground nutmeg, kosher salt and ground black pepper all provide flavor.
  • Cheese: A combination of gruyere and parmesan cheese add dynamic, complex flavor. Make sure you freshly shred the cheese yourself. The pre-package shredded cheeses contain preservatives that prevent it from properly melting.
  • Topping: A combination of crunchy Panko breadcrumbs and buttery pine nuts create a beautiful gratin topping!

Gratin brussels variations

  • Cheese: If you want to swap out the cheeses, you can substitute the parmesan with pecorino romano. The best substitutes for gruyere are Comté, Emmental or Jarlsberg. However, if you are looking for a completely different flavor, you can try Swiss or even cheddar cheese.
  • Bacon: Crispy bacon is an obvious choice if you are looking to take this dish to the next level! Scatter some crispy, crumbled bacon on top of the vegetables before adding the cheese sauce.
  • Pearl Onions: Not a fan of pearl onions? No problem! Simply omit the onions and use more brussels sprouts instead!
  • Double the recipe: Need to feed a more mouths? Wonderful! You can easily double this recipe to feed a crowd!

Overhead photo of the ingredients for au gratin topping - cheese, pine nuts and panko - in a mixing bowl.

FAQs: brussels sprouts gratin

What type of cheese to use in a vegetable gratin?

You can use a wide variety of cheeses for brussel sprout gratin.

While an aged sharp cheddar or semi-soft fontina can work in au gratins, the best combination for brussels sprouts is gruyere and parmesan. Gruyere has a nutty taste with a hint of sweetness and it has wonderful melting properties. And, parmesan has a natural umami flavor and grates beautifully. Together, gruyere and parmesan give the dish a well balanced, complex cheesy flavor!

What is an au gratin pan?

An au gratin pan is a cooking vessel perfectly suited for gratin dishes. Au gratin pans are wide and shallow which expose ingredients more directly to heat.

Gratin pans come in a variety of shapes and sizes from individual servings to larger portions. However, gratin pans are commonly oval and about an inch and a half deep.

What do you use an au gratin pan for?

While au gratin pans are ideal for preparing traditional, oven baked gratins, they are actually quite versatile!

You can use an au gratin pan to cook casseroles, baked pastas, vegetables, pot pies and fish. If you are preparing a dish that requires broiling the top to form a crisp crust, a gratin pan is the perfect vessel!

Photo of gruyere cheese sauce being poured over partially roasted brussels sprout gratin.

What goes with brussels sprout au gratin?

This rich, savory brussels sprout gratin pairs well with a wide variety of dishes! It’s the perfect accompaniment to a vast number of both main dishes and side dishes alike!

Main dishes to pair with brussels sprouts casserole

  • Glazed Ham
  • Pan-Roasted Steak
  • Roasted Pork Tenderloin
  • Short Ribs
  • Roasted Chicken
  • Lamb Chops

Side dishes that pair well with brussels sprouts

Holiday pairing options

This rich and creamy Brussels sprouts recipe is the perfect side dish for your holiday table. I serve these brussels sprouts with the following at Thanksgiving and Christmas.

Photo of freshly baked gratin brussel sprouts topped with parmesan cheese and thyme leaves.

How to make brussels sprouts au gratin?

This dish may look and sound fancy; however, it’s actually very simple and straightforward to prepare!

(Don’t forget to scroll down for the detailed measurements in the complete printable recipe at the bottom of the page.)

  1. Preheat Oven:  Preheat oven to 400 degrees F. Spray a 2 quart gratin or baking dish with non-stick cooking spray. Set aside.
  2. Prepare the topping: In a small mixing bowl, combine the melted butter with the remaining topping ingredients. Set aside.
  3. Par-bake Vegetables:  Line a large, rimmed baking sheet with aluminum foil for easy clean up. Add brussels sprouts and onions. Drizzle with oil and season generously with salt and pepper. Toss to coat. Bake for 15-18 minutes. Remove from oven and transfer to prepared baking dish.
  4. While the vegetables are baking, make the sauce:  In a medium saucepan, melt butter over medium heat. Add the flour and whisk continuously for 1-2 minutes. Add in the cream. Simmer until thickened. Turn off the heat and whisk in both cheeses.
  5. Assemble the gratin: Pour the sauce evenly over the brussels sprouts and onions in the baking dish. Sprinkle the breadcrumb topping evenly over the sauce.
  6. Bake:  Bake gratin, uncovered, for 20-25 minutes minutes, or until the top is golden brown.
  7. Rest and Serve:  Remove the gratin from the oven and place on a wire rack. Allow the gratin sprouts to rest for 5-10 minutes before serving – this gives the brussels a chance to absorb the rich, cheesy sauce. Then, garnish and enjoy!

Making brussel sprouts with cheese: step by step photos

(Don’t forget to scroll down for the in-depth measurements and instructions in the complete printable recipe card at the bottom of the post!)

Step by step photo collage showing how to make Brussels Sprouts au Gratin.

Storing brussels sprouts gratin

Can you make this au gratin recipe in advance?

This brussels sprouts recipe can easily be prepared a day ahead of time!

To make gratin brussels sprout casserole ahead of time

  1. Assemble and bake: Prepare and bake the casserole according to the recipe instructions.
  2. Cool: Allow the dish to cool to room temperature.
  3. Store: Cover the dish with aluminum foil and place in the refrigerator.
  4. Reheat: Uncover the dish and let it sit out on the counter while you preheat an oven to 350°F. Bake for 20-30 minutes, or until warm throughout.

How long will gratin brussels sprout last?

Make sure you allow the brussels sprouts gratin to cool down to room temperature. Either cover the dish with plastic wrap or transfer the leftovers to an airtight container. Properly stored, they will keep up to 5 days in the refrigerator.

Can I freeze this dish?

Brussels sprouts casserole freezes beautifully!

To freeze, prepare and bake the gratin according to the recipe instructions. Allow the dish to cool completely to room temperature. Wrap the dish in a layer of plastic wrap and then wrap in aluminum foil. Brussels sprouts gratin will keep in the freezer for up to 2 months. While you can store the dish for longer, the brussels sprouts will lose flavor and start to get unappetizing and mushy once reheated.

Pro-tip:  Freeze individual sized portions of gratin to have on hand for an easy weeknight side dish!

Close-up photo of the tender roasted brussels sprouts and gruyere cheese sauce in au gratin recipe.

This homemade brussels sprouts au gratin is simple to make and the perfect compliment to any meal! Easy, cheesy and perfectly delicious, this is a recipe your whole family will love!

Until next time, friends, cheers – to stellar side dishes!

Cheyanne

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Recipe testimonials!

Here’s what readers are saying about this easy cheesy brussels sprouts recipe!

  • “Very very good!” – Tina
  • “A delicious new addition to our holiday dinners!” – Wendy

More brussels sprout side dish recipes!

If you love these cheesy sprouts, try one of these delicious recipes next:

The best Brussels Sprouts au Gratin recipe 👇

Overhead photo of freshly baked brussels sprouts casserole in a gratin pan with a glass of white wine and a ramekin of cracked black pepper next to the pan.

Brussels Sprouts Gratin

5 from 8 votes
Author: Cheyanne Holzworth
Total Time: 55 minutes
Prep Time: 15 minutes
Cook Time: 40 minutes
Servings: 6
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This Creamy Roasted Brussels Sprouts Gratin is the perfect holiday side dish! Tender-crisp vegetables are coated in a rich, decadent sauce and topped with a flavorful, crispy topping. This side dish is indulgent, delicious and guaranteed to hit the spot!
Recipe can be scaled up or down by using the slider if you hover your mouse over the number of Servings.

Equipment

  • Au Gratin Pan or 2-Quart Baking Dish
  • Medium Saucepan
  • Small mixing bowl

Ingredients 

  • 1 Pound Brussels Sprouts – trimmed, outer leaves removed & cut in half or quartered (SEE NOTE)
  • 8 ounces Frozen Pearl Onions – thawed & patted dry (SEE NOTES)
  • 2 TBS Olive Oil
  • Kosher Salt & Ground Black Pepper - to taste

Sauce:

Topping:

Instructions

  • Preheat Oven: Arrange oven rack to center position. Preheat oven to 400 degrees F. Spray a 2 quart gratin or baking dish with non-stick cooking spray.  Set aside.
  • Prepare the topping:  In a small mixing bowl, combine the panko, pine nuts, 1/2 cup gruyere, and 1/4 cup parmesan. Season with 1/8 teaspoon of salt and a pinch of pepper. Add in the melted and cooled butter. Stir well to combine.  Set aside.
  • Par-bake Vegetables: Line a large, rimmed baking sheet with aluminum foil for easy clean up. Add brussels sprouts and onions. Drizzle with oil and season with 1/2 teaspoon salt and 1/4 teaspoon of pepper. Toss well to coat. Spread the vegetables out in an even layer.  Bake for 15-20 minutes, tossing halfway through cooking, or until vegetables are almost fork tender. Remove from oven and transfer to prepared baking dish.
  • While the vegetables are baking, Make the Sauce (SEE NOTES):  In a medium-size saucepan, melt the butter over medium heat.  Add the flour and stir continuously for 1-2 minutes or until the mixture is blonde in color. While whisking constantly, gradually add in the cream. Add the nutmeg and season with 1/4 teaspoon of salt and 1/8 teaspoon of pepper. Bring mixture to a gentle simmer and reduce heat as needed to maintain a gentle simmer. Cook, whisking frequently, until the sauce is thickened and coats the back of a spoon, about 5-8 minutes. Turn off the heat. Add in 3/4 cup of gruyere cheese. Whisk until smooth. Add in 1/4 cup parmesan. Whisk until the cheeses are fully incorporated. Taste and adjust for seasoning with salt and pepper.
  • Assemble the gratin:  Pour the sauce evenly over the brussels sprouts and onions in the prepared baking dish. Use a spatula to spread the sauce out in an even layer. Sprinkle the crunchy topping evenly over the sauce. 
  • Bake: Bake gratin UNCOVERED, for 20-25 minutes or until the sauce is bubbling and the top is golden brown.  If the top starts to brown too quickly towards the end of baking, lightly tent the dish with aluminum foil. 
  • Rest and Serve:  Allow to rest for 5 minutes before serving.  Garnish with more parmesan and fresh thyme! Enjoy!

Video

Notes

  1. Brussels Sprouts: You want the brussels sprouts to be uniform in size. If the brussels sprouts are huge, quarter them.  If they are on the medium or small side, half them. You want them to be roughly the same size as the onions. 
  2. Onions: Frozen pearl onions are so much more convenient than fresh! Thaw the completely in the refrigerator overnight. Pat them thoroughly dry before proceeding with the recipe. 
  3. Cream: To ensure your sauce is lump-free, make sure you use room temperature (or close to it) heavy cream. Remove the cream from your refrigerator and let it sit on the counter while you prep all the ingredients.
  4. The Creamy Sauce: Make sure you slowly whisk the cream into the roux (butter and flour mixture). Do this by adding the cream a little bit at a time, whisking until smooth between each addition. This will ensure your sauce is silky and thick! 
  5. Want to add Bacon? You can easily add bacon if desired!  Scatter cooked, crumbled bacon on top of the par-roasted brussels sprouts and onions in the baking dish. Then, pour on the cheese sauce and top with crispy topping. 
Nutritional information is an approximation based upon 6 servings.  Exact information will depend upon the brands of ingredients and precise measurements used.

Nutrition

Calories: 273kcal    Carbohydrates: 20g    Protein: 6g    Fat: 19g    Saturated Fat: 9g    Cholesterol: 40mg    Sodium: 129mg    Potassium: 480mg    Fiber: 4g    Sugar: 4g    Vitamin A: 1025IU    Vitamin C: 69.1mg    Calcium: 122mg    Iron: 2mg
Course: Side Dish
Cuisine: American, French, Fusion

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Brussels Sprouts & Pearl Onion Gratin