Let’s talk about comfort food with an elegant twist—Brussel Sprouts Au Gratin. Imagine beautifully roasted, tender brussels sprouts blanketed in a luscious, melty cheese sauce with subtle hints of mustard and onion that elevate this humble veggie to a true weeknight rock star. The crisp golden top makes each forkful irresistible. What’s even better? It’s wonderfully easy to whip up and so forgiving, even for beginners. If you need a side dish that wows but won’t have you sweating over the stove, this is it!

Why You’ll Love This Recipe

  • Effortless and Fast: A quick cheese sauce comes together in minutes, and the oven does the rest. Hands-off after prep!
  • Flavorful and Satisfying: Rich, cheesy goodness meets the earthy crunch of brussels sprouts. This is ultimate comfort food territory.
  • Crowd-Pleaser: Even people on the fence about brussels sprouts will find themselves asking for seconds.
  • Customizable: Make it your own with simple swaps or additions, whether cheese blends, spices, or veggie add-ins.

Ingredients You’ll Need

There’s nothing complicated here—just classic, craveable flavors with a cheesy backbone. Here’s what you’ll gather:

  • Butter: The base for your roux; adds richness and helps create a silky sauce.
  • All-Purpose Flour: Essential to thicken the cheese sauce, ensuring it clings to every bite.
  • Ground Mustard: Gives a tangy undertone and complexity to the sauce. If you love Dijon, you could use a dab instead.
  • Onion Powder: For gentle, savory depth without extra chopping.
  • Salt: Enhances flavor and balances the richness of the cheese.
  • Milk: Brings the sauce together—whole milk creates a creamier texture, but any milk works in a pinch.
  • Cream Cheese: Provides lushness and a slight tang, helping the sauce become ultra-smooth.
  • Parmesan Cheese: Sharp, nutty, and perfectly melty. This is non-negotiable for that signature Au Gratin effect!
  • Brussels Sprouts: The real star. When roasted in creamy cheese sauce, they turn sweet and buttery. If some are larger, halve them for even cooking and maximum sauce coverage!

Note: You’ll find the complete list of ingredients, along with their exact measurements, in the printable recipe card at the bottom of this post.

Variations

This dish is made for customizing! Here are some inspired ideas:

  • Cheese Swap: Try a mix of sharp cheddar, Gruyère, or Swiss for a more pronounced flavor or gooey texture.
  • Spice It Up: Add a pinch of cayenne or nutmeg to the sauce for warmth.
  • Breadcrumb Topping: Scatter some golden panko or regular breadcrumbs over the top before baking for extra crunch.
  • Add Protein: Stir in cooked, crumbled bacon or shredded rotisserie chicken right before baking for a heartier take.
  • Veggie Boost: Mix in caramelized onions or sautéed mushrooms to up the umami factor.

How to Make Brussel Sprouts Au Gratin

The steps are straight-forward, and there’s no need to fuss. Here’s what you’ll do:

Step 1: Prep the Oven and Veggies

Preheat the oven to 350°F. Lightly grease an 8×8-inch casserole dish with nonstick spray. Trim the brussels sprouts—make sure any oversized ones are halved to help them cook uniformly and absorb the sauce.

Step 2: Make the Cheese Sauce

In a medium saucepan over medium heat, melt butter. Whisk in the flour to create a smooth roux. Sprinkle in mustard powder, onion powder, and salt. Stir until bubbly and fragrant, about a minute.

Slowly pour in the milk while whisking to avoid lumps. The sauce will thicken after a few minutes—keep whisking and be patient! Once thick, take the pan off the heat, add cream cheese and parmesan, and stir until fully melted and silky smooth.

Step 3: Assemble and Bake

Arrange the brussels sprouts in your prepared dish. Pour the cheese sauce evenly over the top, letting it settle into all the nooks. Slide the dish into the oven and bake for 45 minutes to 1 hour. The sprouts should be fork-tender and the top golden and bubbly.

Pro Tips for Making the Recipe

  • Even Sizing: Halve any overly large brussels sprouts so they cook through and soak up the sauce.
  • No Lumpy Sauce: Pour milk in gradually and whisk continuously to keep the cheese sauce velvety smooth.
  • Amp It Up: For a deeper flavor, try roasting brussels sprouts for 10 minutes on a sheet pan before assembling. This caramelizes them slightly.
  • Big Batch Friendly: Double everything for a crowd—just use a larger casserole pan and keep an eye on baking time.

How to Serve

This dish deserves to be the star of any dinner spread, but it also plays well as a sidekick:

Pairing Ideas:

  • Main Dish: Wonderful alongside roasted chicken, seared steak, or baked fish.
  • Vegetarian Plate: Pair with quinoa, warm lentil salad, or a big crunchy green salad to keep things light and complete.
  • Holiday Table: This is perfect for Thanksgiving, Christmas, or any cozy gathering.

Garnish:

Scatter fresh parsley or thyme over the gratin for a pop of color and herbal brightness.

Make Ahead and Storage

Storing Leftovers

Store leftovers in an airtight container in the refrigerator for up to three days. The flavors deepen overnight!

Freezing

Freeze individual portions in freezer-safe containers for up to two months. Thaw in the fridge overnight before reheating.

Reheating

Reheat in a 350°F oven until warm and bubbly, or use the microwave for quick lunches (add a splash of milk if it seems dry).

FAQs

  1. Can I use frozen brussels sprouts?

    Absolutely. Thaw and drain them well to avoid excess water in the dish. The texture will be softer, but the cheesy goodness will remain.

  2. What’s the best cheese for an ultra-creamy gratin?

    Parmesan is classic, but for extra creaminess, add some shredded Gruyère or a handful of sharp cheddar to the sauce.

  3. Can this be prepped ahead?

    Yes—assemble everything up until baking, cover, and refrigerate for up to 24 hours. When ready, bake as directed (you might need an extra 10 minutes if it goes in cold).

  4. Are there gluten-free options?

    Certainly! Use a 1:1 gluten-free flour blend in the roux or try cornstarch (use half the amount), and double-check your cheese for hidden gluten.

Final Thoughts

Brussel Sprouts Au Gratin transforms everyday ingredients into a decadent dish that feels like a treat—without the stress. Whether you’re planning a weeknight dinner or a special celebration, this recipe promises creamy, cheesy, golden perfection every time. It’s time to grab those brussels sprouts and show everyone just how delicious they can be!

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Brussel Sprouts Au Gratin Recipe

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  • Author: Julia
  • Prep Time: 10 minutes
  • Cook Time: 1 hour
  • Total Time: 1 hour 10 minutes
  • Yield: 6 servings 1x
  • Category: Side-dishes
  • Method: Baking
  • Cuisine: American
  • Diet: Vegetarian
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Description

Brussel Sprouts Au Gratin is a creamy and cheesy casserole dish featuring tender Brussels sprouts baked in a luscious cheese sauce. It’s a flavorful and comforting side, perfect for holiday tables or weeknight dinners alike.

Ingredients

Units Scale

For the Cheese Sauce

  • 2 tablespoons butter
  • 2 tablespoons all-purpose flour
  • 1/2 teaspoon ground mustard
  • 1/2 teaspoon onion powder
  • 1/2 teaspoon salt
  • 1 1/2 cups milk
  • 3 tablespoons cream cheese
  • 1/2 cup shredded parmesan cheese

For the Casserole

  • 1 to 1 1/2 pounds Brussels sprouts, trimmed (halve if large)
  • Nonstick cooking spray (for greasing the pan)

Instructions

  1. Prepare the Oven and Dish: Preheat your oven to 350°F (175°C). Lightly grease a 2-quart (8×8-inch) casserole dish with nonstick cooking spray to prevent sticking.
  2. Make the Roux: In a medium saucepan over medium heat, melt the butter. Whisk in the flour to create a smooth roux. Add ground mustard, onion powder, and salt, whisking until incorporated.
  3. Thicken the Sauce: When the roux is warm and bubbly, slowly pour in the milk, whisking continuously. Continue heating and stirring until the mixture thickens and coats the back of a spoon.
  4. Add Cheese: Remove the saucepan from heat. Stir in cream cheese and shredded parmesan cheese until both are melted and the sauce is smooth and creamy.
  5. Assemble the Casserole: Place the trimmed (and halved if large) Brussels sprouts in the prepared casserole dish. Pour the cheese sauce evenly over the sprouts, making sure they are well coated.
  6. Bake: Transfer the dish to the preheated oven and bake for 45 minutes to 1 hour, until the Brussels sprouts are tender and the top is golden and bubbly.
  7. Serve: Allow the casserole to cool slightly before serving. Enjoy as a flavorful side dish.

Notes

  • If your Brussels sprouts are particularly large, cut them in half for even cooking and easier eating.
  • For extra flavor, top with additional parmesan or breadcrumbs during the last 10 minutes of baking.
  • This dish can be prepped ahead and baked right before serving.
  • Leftovers can be stored in the refrigerator for up to 3 days and reheated in the oven or microwave.

Nutrition

  • Serving Size: 1/6 of recipe
  • Calories: 210 kcal
  • Sugar: 5g
  • Sodium: 522mg
  • Fat: 9g
  • Saturated Fat: 5g
  • Unsaturated Fat: 4g
  • Trans Fat: 0g
  • Carbohydrates: 19g
  • Fiber: 2g
  • Protein: 13g
  • Cholesterol: 28mg
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Hi, I’m Julia! A foodie who believes in keeping cooking simple, fun, and full of flavor. From quick weeknight meals to tasty treats, I’m here to share recipes that make life a little easier—and a lot more delicious. Let’s get cooking!

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