This Creamy Brussels Sprouts au Gratin recipe 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 sprinkled with a buttery, crunchy topping! This restaurant-worthy brussels sprouts casserole is the perfect easy and delicious side dish – and it’s guaranteed to become a family favorite!
This rich and creamy Brussels sprouts recipe is the perfect side dish for family dinners, or a delicious addition to your holiday table! It goes perfectly with turkey breast roulade, chestnut stuffing, your favorite cranberry sauce and homemade rolls! Or, serve it with grilled steaks and sautéed mushrooms for a cozy weeknight dinner!
Update: This post was originally published in November 2014. I’ve made updates to the post below to include new photos and more information about brussels sprout gratin. Plus, I’ve included in-depth step-by-step photos and a recipe video to show you how easy this brussels sprout casserole is to prepare!
Hi friends! Are you ready for the creamiest, dreamiest, most swoon-worthy side?
Todays dish 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!
Brussels Sprouts Gratin: recipe overview
This recipe features simply roasted, tender brussels sprouts and sweet pearl onions smothered with a creamy, rich cheese sauce and sprinkled with a crunchy, buttery topping. Baked until golden brown and bubbly around the edges, this dish is so delicious even the brussels sprouts haters will ask for seconds (or thirds)!
The brussels sprouts in this gratin are nothing like the memories you hold of your grandmother’s or mother’s sprouts (no offense). You know those over-cooked, mushy, sad and lifeless sprouts. These brussels sprouts are everything a vegetable should be – they’re perfectly tender-crisp, flavorful and highly addictive!!
I pinkie promise you will love these sensational sprouts! If you plan on having a brussels sprouts 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, be prepared for your mind to be blown! There is a very good chance this dish will even transform you into a brussels sprouts addict for life!
Why this recipe works
- Infusing the cream sauce with aromatics adds extra flavor.
- Partially roasting the brussels sprouts before assembling the gratin ensures they are perfectly tender-crisp.
- Baking the gratin uncovered allows the cream sauce to continue thickening and beautifully coat the vegetables.
- Allowing the gratin to rest for 5-10 minutes before serving gives the brussels sprouts a chance to absorb the rich, cheesy sauce.
What is brussels sprouts au gratin?
Brussels sprouts au gratin is an indulgent baked dish similar to a casserole. It features partially cooked brussels sprouts topped with a white cheese sauce, then sprinkled with a breadcrumb topping and baked 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 it?
You can pronounce au gratin as oh-gra-tan or aw-graht-n.
What ingredients do I need?
This easy brussels sprout side dish is rich and bursting with flavor! This 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!
- 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!
What type of cheese to use in a vegetable gratin?
You can use a wide variety of cheeses for brussels sprouts 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 au 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!
What goes with cheesy brussels sprouts?
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 au gratin
- Roasted Turkey
- Glazed Ham
- Pan-Roasted Steak
- Roasted Pork Tenderloin
- Short Ribs
- Roast Beef or Rib Roast
- Roasted Chicken
- Lamb Chops
Side dishes that pair well with brussels sprouts gratin
- Soft Dinner Rolls
- Roasted Mushrooms
- Stuffing or Dressing
- Roasted Potatoes
- Green Beans
- Corn Casserole
- Sweet Potatoes
- Roasted Broccoli
- Wild Rice Salad
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.)
- Preheat Oven: 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 melted butter with the remaining topping ingredients. 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 generously with salt and pepper. Toss to coat. Bake for 15-18 minutes. Remove from oven and transfer to prepared baking dish.
- 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.
- 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.
- Bake: Bake gratin, uncovered, for 20-25 minutes minutes, or until the top is golden brown.
- Rest and Serve: Remove the gratin from the oven. Let it rest for 5-10 minutes before serving. Garnish and enjoy!
How to make brussels sprouts gratin 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!)
Tips for making ahead and freezing gratin
Can you make brussels sprouts au gratin in advance?
This brussels sprouts recipe can easily be prepared a day ahead of time!
To make brussels sprout casserole in advance
- Assemble and bake: Prepare and bake the casserole according to the recipe instructions.
- Cool: Allow the dish to cool to room temperature.
- Store: Cover the dish with aluminum foil and place in the refrigerator.
- 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 it 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 you freeze it?
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!
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!
Recipe testimonials – What people are saying about this recipe
Here’s what readers are saying about this easy cheesy brussels sprouts casserole!
- “Very very good!” –Tina
- “A delicious new addition to our holiday dinners!” –Wendy
- “Outrageously delicious! Thank you for sharing this recipe!” –Suzanna
Looking for more brussels sprouts recipes?
If you love these cheesy sprouts, try one of these delicious recipes next:
The best Brussels Sprouts au Gratin recipe 👇
Brussels Sprouts Gratin
- Au Gratin Pan or 2-Quart Baking Dish
- Medium Saucepan
- Small mixing bowl
- 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
- 2 TBS Unsalted Butter
- 1 Clove Garlic - thinly sliced
- 2 tsp fresh Thyme Leaves - roughly chopped
- 2 TBS All Purpose Flour
- 2 Cups Heavy Cream - at room temperature (SEE NOTES)
- 1/8 tsp Ground Nutmeg
- 1 1/4 Cup Shredded Gruyere Cheese - DIVIDED (about 4 ounces)
- 1/2 Cup Shredded Parmesan Cheese - DIVIDED (about 1.7 ounces), plus more for serving
- 2 TBS Unsalted Butter - melted & cooled
- 2/3 Cup Panko Bread Crumbs (can substitute fresh bread crumbs)
- ¼ Cup Pine Nuts – roughly chopped
- 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!
- 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.
- 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.
- 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.
- 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!
- 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.
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