Servings
Font
Back
5.0 from 9 votes

Mushroom & Brussels Sprouts Au Gratin with Crispy Parmesan Walnut Panko ‘Fried’ Onion

Wonderful mushroom and brussels sprouts au gratin with a luscious, creamy cheese sauce and a crispy parmesan walnut "fried" onion topping. This unique twist on traditional au gratin recipes is full of delicious, savory flavors you'll love. Perfect for Thanksgiving or pairing with weeknight dinners!

Prep Time
15 mins
Cook Time
1 hr 15 mins
Total Time
1 hr 25 mins
Servings: 12 servings
Calories: 226 kcal
Course: Side Dish
Cuisine: American , Vegan

Ingredients

  • Brussels Sprouts and Onions:
  • 2 pounds Brussels sprouts, trimmed, outer leaves removed and sliced in half
  • 1 tablespoon salted butter, melted
  • 2 yellow onions, thinly sliced
  • ½ cup panko bread crumbs, gluten-free if desired
  • ½ cup grated Parmesan cheese
  • ½ cup very finely chopped raw walnuts
  • ½ teaspoon garlic powder
  • ½ teaspoon kosher salt
  • Mushrooms:
  • 1 tablespoon salted butter
  • 16 ounces baby bella mushrooms, sliced
  • ¼ teaspoon kosher salt
  • freshly ground black pepper
  • 1 tablespoon fresh thyme leaves
  • ¼ teaspoon red pepper flakes
  • 3 garlic cloves, minced
  • Sauce:
  • ¼ cup salted butter
  • ⅓ cup all-purpose flour (or 1:1 gluten-free all-purpose flour)
  • 1 ½ cups low-sodium chicken broth (or vegetable broth), plus another ½ cup more, if necessary
  • 1 cup whole milk or unsweetened almond milk
  • ½ cup grated Parmesan cheese
  • 4 ounces gruyere cheese, shredded
  • ½ teaspoon kosher salt, plus more to taste
  • Lots of freshly ground black pepper

Instructions

    Cup of Yum
  1. Preheat the oven to 375°F. Grease a 2-quart baking dish or 9x13-inch baking pan.
  2. Prepare the Brussels sprouts: Bring a large pot of generously salted water to a boil over high heat. Add the brussels sprouts and blanch, 2 minutes. Drain brussels and run under VERY cold water to stop the cooking process. Set aside.
  3. Prepare the onions: In a large skillet, melt the butter over medium heat. Add the onions and cook until softened, about 8 minutes. Transfer the onions to a large bowl and add the panko bread crumbs, parmesan cheese, walnuts, garlic powder, and salt; toss well to coat the onions. Set aside.
  4. Cook the mushrooms: Return the same large skillet to medium heat and melt the butter. Add the mushrooms, salt, and pepper. Cook mushrooms, stirring occasionally, until all liquid is absorbed from mushrooms and they are golden brown; 8 to 10 minutes. Stir in the thyme, red pepper flakes and garlic and cook, stirring until fragrant, 1 minute. Transfer to the baking pan with the Brussels sprouts and toss to combine.
  5. Prepare the sauce: Return the same large skillet to medium heat and melt the butter. Whisk in the flour and cook until a paste forms, then slowly stream in the broth and then the milk, constantly whisking away any lumps, until smooth and well-combined. Increase heat and bring mixture to a boil, then reduce the heat to medium-low and simmer, whisking occasionally, until sauce thickens to the consistency of gravy, 5 minutes. (If the sauce gets too thick, you can add up to ½ cup more broth.) Remove from heat and stir in the parmesan, gruyere, salt, and pepper. Taste and adjust seasoning if necessary.
  6. Pour the sauce over the Brussels and mushrooms and give it a gentle stir to coat the brussels and mushrooms. Evenly distribute the onion mixture over the top. Bake, uncovered, until the topping is golden brown and the sauce is bubbly, 25 to 35 minutes.

Notes

  • See the full post for tips, tricks, and great ways to customize this recipe!

Nutrition Information

Serving 1serving (based on 12) Calories 226cal (11%) Carbohydrates 16.1g (5%) Protein 11.1g (22%) Fat 14.5g (22%) Saturated Fat 6.3g (32%) Fiber 4.1g (16%) Sugar 3.6g (7%)

Nutrition Facts

Serving: 12servings

Amount Per Serving

Calories 226

% Daily Value*

Serving 1serving (based on 12)
Calories 226cal 11%
Carbohydrates 16.1g 5%
Protein 11.1g 22%
Fat 14.5g 22%
Saturated Fat 6.3g 32%
Fiber 4.1g 16%
Sugar 3.6g 7%

* Percent Daily Values are based on a 2,000 calorie diet.