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Brussels Sprouts Au Gratin

Brussels sprouts au gratin are always on the menu for the holidays. Made with roasted Brussels sprouts tossed with a creamy cheese sauce, and baked with melty Gruyere and parmesan on top.
Prep Time15 mins
Cook Time45 mins
Total Time1 hr
Course: Side Dish
Cuisine: American
Keyword: brussels sprouts gratin
Servings: 6 people
Author: Tania


  • 1.5 pounds fresh Brussels sprouts, trimmed and halved lengthwise
  • Salt and pepper
  • 3 cloves garlic, minced
  • Olive oil
  • 2 tablespoons unsalted butter
  • 2 tablespoons all-purpose flour
  • 1 ¼ cups whole milk (plus more as needed)
  • 1 cup shredded or grated Gruyere cheese, divided
  • ½ cup shredded parmesan cheese
  • cup crumbled cooked bacon (plus more for garnish)


Roast the Brussels Sprouts

  • Preheat oven to 400 degrees Fahrenheit.
  • On a large sheet pan, toss the Brussels sprouts with the minced garlic, a few drizzles of olive oil, about ¼ teaspoon of salt, and a few grinds of black pepper. Roast for 20 minutes at 400 degrees Fahrenheit, flipping halfway through. Tip: Don't overcrowd the pan. Use two sheet pans if needed.

Make the Cheese Sauce

  • Meanwhile, make the cheese sauce. In a medium pot, melt the butter over medium heat. Once melted, add the flour and whisk constantly for about 3-4 minutes, until thickened. This is called a roux. At this point, it should be a bit pale in color and begin to smell a tiny bit toasty.
  • Then, gradually add the milk, breaking up the roux with a wooden spoon. Simmer for a few minutes until thickened.
  • Add ½ cup of the gruyere cheese and stir until melted. Add more milk if needed until desired consistency. Season with salt and pepper to taste. Turn off the heat.

Assemble and Bake

  • Toss the roasted Brussels sprouts with the cheese sauce and the bacon until combined. Transfer to a baking dish. Sprinkle with the remaining ½ cup of gruyere cheese, the parmesan cheese, and more bacon bits.
  • Bake at 400 degrees Fahrenheit for 15-18 minutes until bubbly and golden brown. If desired, broil for 1-2 minutes additional minutes to get a deeper golden brown color. Serve immediately. Enjoy!


  • Special equipment: box grater, baking dish, sheet pans.
  • Make ahead: Cook the bacon in advance. Trim and halve the Brussels sprouts in advance. Grate or shred the cheese in advance. Make the cheese sauce 1 day ahead.
  • Cheese sauce: It can be made 1 day in advance. Refrigerate, and warm it up in a saucepan prior to using.
  • Storing: Refrigerate for up to 3 days. Reheat in the microwave oven.