Cheesy Brussels Sprouts au Gratin

This cheesy Brussels sprouts au gratin comes together in about 40 minutes with a creamy Gruyere sauce, roasted Brussels sprouts, and tender leeks. It’s the perfect easy side dish for holiday dinners or cozy weeknights!

Easy Cheesy Brussels Sprouts Au Gratin Recipe

• Takes just 40 minutes from start to finish – and for most of that time, the oven is doing all the work! – for an effortless side dish.
• Creamy, cheesy, and loaded with flavor. Even Brussels sprouts skeptics will love this side dish!

Ingredients for Cheesy Brussels Sprouts Au Gratin

• Brussels Sprouts: The star of the dish! Roasted until tender and slightly crisp before being baked in a delicious cheese sauce.
• Butter: Adds richness to the sauce and helps sauté the leeks. Salted or unsalted will work.
• Leek: Offers a delicate onion flavor that pairs beautifully with creamy cheese. Substitute with a small yellow onion or a couple of shallots.
• Garlic: Adds depth and savory aroma. Fresh is best, but 1/2 a teaspoon of garlic powder works in a pinch too.
• Flour: Thickens the cheese sauce to a smooth, creamy consistency. Stick with all-purpose for this au gratin.
• Heavy Cream: Creates the luxurious texture of the gratin sauce. For a lighter option, use half and half but it will make the consistency of the sauce thinner.
• Dijon Mustard: Adds tang and complexity to the cheese sauce. You can use whole grain mustard or omit if preferred.
• Dried Thyme: Brings an earthy herbal note. Italian seasoning or dried oregano also work well.
• Rubbed Sage: Complements the leeks and cheese with warm, savory flavor. Sub with poultry seasoning if needed.
• Gruyere Cheese: Melts beautifully and gives a nutty, creamy finish. Swiss or sharp white cheddar are great alternatives.

How to Make Cheesy Brussels Sprouts Au Gratin

Roast the Brussels Sprouts: Heat oven to 400 degrees. Add trimmed and halved Brussels sprouts to your baking dish, drizzle with olive oil, and season with salt and pepper. Toss to coat evenly and roast for 15 minutes.

Sauté the Leeks: While the sprouts roast, melt butter in a large sauté pan over medium heat. Add sliced leeks with a pinch of salt and pepper. Cook, stirring frequently, for 3–4 minutes until softened. Stir in minced garlic and cook for 1 minute, then add flour and cook another minute, stirring frequently.

Make the Sauce: Whisk in heavy cream, Dijon, thyme, sage, and a couple pinches of salt and pepper. Cook for 2–3 minutes until slightly thickened. Stir in half the shredded cheese until melted and smooth. Taste and adjust seasoning.

Combine: Pour the cheese sauce over the roasted Brussels sprouts and toss gently to coat.

Top. Sprinkle the remaining cheese on top.

Bake and Serve. Bake for 15–20 minutes, until bubbly and golden brown. Enjoy!

Tips for Making Cheesy Brussels Sprouts Au Gratin

• Roast the Brussels sprouts first for the best flavor and texture before adding the cheese sauce.
• Shred the cheese yourself. Pre-shredded cheese often contains anti-caking agents that prevent smooth melting.
• For extra golden color, broil for 1–2 minutes at the end, watching closely.

Make-Ahead Instructions

• Prepare the side dish through step #8 (just before baking). Cover and store in the fridge overnight.
• Let the dish sit out on the counter for 30 minutes before baking according to the recipe instructions.
• Plan to add some extra cooking time to account for the colder temperature.

Storing Leftovers

Store any leftovers in an airtight container in the refrigerator for up to 3 days.

Reheating Cheesy Brussels Sprouts Au Gratin

• Reheat in a 350 degree oven for 15–20 minutes until warmed through.
• You can also microwave single portions in 30-second intervals, stirring occasionally.
• Season to taste with salt and pepper before serving.

Serving Suggestions

• honey glazed crock pot ham
• braised beef short ribs
• Dutch oven pot roast
• slow cooker country style ribs
• oven braised chuck roast

Try these easy side dishes next!