Mushroom & Brussels Sprouts Au Gratin


Each single yr I discover a option to outdo myself at Thanksgiving. Whereas I completely admire all the classics – particularly my mother-in-law’s heavenly mashed potatoes – I additionally take nice pleasure in placing one thing new and totally different on the desk. See for your self in my final Thanksgiving roundup!

This beautiful mushroom and brussels sprouts au gratin is an upgraded model of the inexperienced bean casserole everyone knows and love. It’s bought all of the issues: brussels sprouts that soften in your mouth, toasty thyme-infused buttery mushrooms, and a next-level “fried” onion and walnut topping.

Sure, it’s going to be a showstopper in your Thanksgiving desk, however don’t anticipate Thanksgiving to attempt it! It will be an excellent pairing together with your Sunday evening roasted rooster. My gosh, you’re going to like it! Byeeeee inexperienced beans.

mushroom and brussels sprouts au gratin in a pan

Components on this mushroom and brussels sprouts au gratin

Tender brussels sprouts, savory mushrooms, crispy onions, and a creamy parmesan-gruyere cheese sauce — this au gratin recipe is mindblowly scrumptious. We’re skipping the cream of mushroom soup right here, individuals! Right here’s what you’ll have to make it:

  • Veggies: you’ll want contemporary brussels sprouts, yellow onions, and child bella mushrooms for this au gratin recipe.
  • Butter: we’re including salted butter to cook dinner down the veggies and to begin the cheese sauce.
  • For the crispy onions: you’ll be tossing the onions in a mix of panko bread crumbs, parmesan cheese, chopped walnuts (the important thing for additional crunch!), garlic powder, and salt.
  • For the mushrooms: cook dinner down these beautiful mushrooms with butter, salt, pepper, contemporary thyme, pink pepper flakes, and garlic.
  • For the sauce: the silky, savory sauce is made with butter, all-purpose flour, low-sodium rooster broth, milk, parmesan cheese, gruyere, salt & pepper.

crispy onion topping in a bowl for brussels sprouts gratin

Customise this brussels sprouts gratin

Sure, there are straightforward methods to make this au gratin your individual! Right here’s what I can advocate:

  • Make it gluten-free. Merely use gluten free bread crumbs and a 1:1 gluten free all goal flour.
  • Hold it vegetarian. Go for vegetable broth rather than the rooster broth.
  • Select your cheese. I like the combo of parmesan and gruyere cheese, however you might additionally use cheddar, fontina, or a smoky gouda!
  • Go nut free. I like the additional crispiness that chopped walnuts add to the crispy onions, however in case you’re nut free you possibly can merely add extra bread crumbs.

mushrooms and brussels sprouts in a baking pan to make brussels sprouts gratin

Searching for an additional savory kick?

If you happen to’re not serving vegetarians I recommend including cooked bacon or ham for additional scrumptious savory taste!

unbaked brussels sprouts mushroom au gratin in a baking pan

Tips on how to make this brussels sprouts and mushroom au gratin

  1. Prep the brussels sprouts. Begin by blanching the brussels sprouts, then draining them and working them beneath very chilly water in order that they cease cooking.
  2. Prep the onions. Prepare dinner the onions down in slightly butter, then toss them with panko bread crumbs, parmesan, walnuts, garlic powder, and salt.
  3. Prepare dinner the mushrooms. Subsequent, cook dinner the mushrooms with butter in the identical skillet the onions have been in till they’re good and golden. Then stir within the thyme, pink pepper flakes, and garlic. Add them to the baking pan with the brussels sprouts.
  4. Make the sauce. Soften butter in the identical skillet, whisk within the flour till a paste varieties, then slowly stream within the broth and milk and whisk till effectively mixed. Deliver the combination to a boil, then scale back to a simmer and let it thicken to a gravy texture. Take away it from the warmth and stir within the parmesan, gruyere, salt & pepper. Style and modify the seasonings.
  5. Pour, prime & bake. Pour the cheese sauce into the pan with the brussels sprouts and mushrooms and stir to coat the whole lot. Evenly prime the pan with the onions, bake it up till golden brown and bubbly, and luxuriate in!

mushroom and brussels sprouts au gratin in a baking pan

Make it forward of time

You possibly can simply make this brussels sprouts gratin forward to save lots of time throughout Thanksgiving. Right here’s what I like to recommend:

  1. Put together the recipe as directed however don’t bake it. Wrap the casserole dish in foil and place it within the fridge as much as 2 days forward.
  2. As soon as prepared, take away the foil and bake the au gratin till the onions are good and golden brown and the sauce is bubbly.
  3. Serve instantly with all of your favourite Thanksgiving dishes!

brussels sprouts and mushroom gratin in a baking pan

Storing & reheating suggestions

  • To retailer: merely retailer this broccoli cauliflower gratin within the fridge in particular person, hermetic containers or cowl the complete pan and place it within the fridge. It should keep good for as much as 5 days.
  • To reheat: reheat particular person parts within the microwave or place the pan again within the oven till heated by means of.

mushroom brussels sprouts au gratin in a baking pan and on a plate

Extra Thanksgiving recipes you’ll love

Get all of my Thanksgiving recipes right here!

I hope you like this mushroom and brussels sprouts au gratin! If you happen to make it be sure you go away a remark and a score so I understand how you appreciated it. Get pleasure from, xo!

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

brussels sprouts gratin in a baking dish and on a plate

Prep Time 15 minutes

Prepare dinner Time 1 hour 10 minutes

Complete Time 1 hour 25 minutes

Serves12 servings

Fantastic mushroom and brussels sprouts au gratin with a luscious, creamy cheese sauce and a crispy parmesan walnut “fried” onion topping. This distinctive twist on conventional au gratin recipes is stuffed with scrumptious, savory flavors you will love. Excellent for Thanksgiving or pairing with weeknight dinners!


  • Brussels Sprouts and Onions:
  • 2 kilos Brussels sprouts, trimmed, outer leaves eliminated 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 uncooked walnuts
  • ½ teaspoon garlic powder
  • ½ teaspoon kosher salt
  • Mushrooms:
  • 1 tablespoon salted butter
  • 16 ounces child bella mushrooms, sliced
  • ¼ teaspoon kosher salt
  • Freshly floor black pepper
  • 1 tablespoon contemporary thyme leaves
  • ¼ teaspoon pink pepper flakes
  • 3 garlic cloves, minced
  • Sauce:
  • ¼ cup salted butter
  • cup all-purpose flour (or 1:1 gluten-free all-purpose flour)
  • 1 ½ cups low-sodium rooster broth (or vegetable broth), plus one other ½ cup extra, if needed
  • 1 cup complete milk or unsweetened almond milk
  • ½ cup grated parmesan cheese
  • 4 ounces gruyere cheese, shredded
  • ½ teaspoon kosher salt, plus extra to style
  • Numerous freshly floor black pepper


  • Preheat the oven to 375°F. Grease a 2-quart baking dish or 9×13-inch baking pan.

  • Put together the Brussels sprouts: Deliver a big pot of generously salted water to a boil over excessive warmth. Add the brussels sprouts and blanch, 2 minutes. Drain brussels and run beneath VERY chilly water to cease the cooking course of. Put aside.

  • Put together the onions: In a big skillet, soften the butter over medium warmth. Add the onions and cook dinner till softened, about 8 minutes. Switch the onions to a big bowl and add the panko bread crumbs, parmesan cheese, walnuts, garlic powder, and salt; toss effectively to coat the onions. Put aside.

  • Prepare dinner the mushrooms: Return the identical giant skillet to medium warmth and soften the butter. Add the mushrooms, salt, and pepper. Prepare dinner mushrooms, stirring sometimes, till all liquid is absorbed from mushrooms and they’re golden brown; 8 to 10 minutes. Stir within the thyme, pink pepper flakes and garlic and cook dinner, stirring till aromatic, 1 minute. Switch to the baking pan with the Brussels sprouts and toss to mix.

  • Put together the sauce: Return the identical giant skillet to medium warmth and soften the butter. Whisk within the flour and cook dinner till a paste varieties, then slowly stream within the broth after which the milk, continuously whisking away any lumps, till easy and well-combined. Enhance warmth and produce combination to a boil, then scale back the warmth to medium-low and simmer, whisking sometimes, till sauce thickens to the consistency of gravy, 5 minutes. (If the sauce will get too thick, you possibly can add as much as ½ cup extra broth.) Take away from warmth and stir within the parmesan, gruyere, salt, and pepper. Style and modify seasoning if needed.

  • Pour the sauce over the Brussels and mushrooms and provides it a mild stir to coat the brussels and mushrooms. Evenly distribute the onion combination excessive. Bake, uncovered, till the topping is golden brown and the sauce is bubbly, 25 to 35 minutes.

Recipe Notes

See the total submit for suggestions, tips, and nice methods to customise this recipe!


Serving: 1serving (primarily based on 12)Energy: 226calCarbohydrates: 16.1gProtein: 11.1gFats: 14.5gSaturated Fats: 6.3gFiber: 4.1gSugar: 3.6g


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