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+ servings

Brussels Sprouts and Mushroom Casserole

This brussels sprouts and mushroom casserole topped with french fried onions is a twist on the Thanksgiving staple and one you have to try!
scooping brussels sprout and mushroom casserole out of baking dish
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4.5 from 4 votes


  • 8 tablespoons butter , divided
  • 1 ½ lb brussels sprouts , halved
  • 8 oz cremini or baby bella mushrooms , halved or quartered
  • ½ onion , chopped
  • 2 cloves of garlic , minced
  • 2 tablespoons all-purpose flour
  • 1 cup chicken or vegetable broth
  • 1 cup half and half
  • 1 cup panko breadcrumbs
  • 6 oz can of French fried onions
  • Salt and pepper , to taste


  • Preheat oven to 375°F. Grease a 9x13 inch casserole dish with butter or nonstick spray.
  • Melt 2 tablespoons of butter in a large skillet set over medium heat. Add brussels sprouts and cook until browned, about 5 minutes. Transfer to a separate bowl and set aside.
  • Add another 2 tablespoons of butter, mushrooms and onions to the skillet, season with salt and pepper, and cook until soft, about 5-6 minutes. Add garlic and cook for 1 minute more. Add to the bowl with the brussels sprouts.
  • Melt 2 tablespoons of butter in skillet. Add flour and whisk to form a thick paste. Add chicken or vegetable broth gradually while whisking constantly. Whisk in half and half. Increase heat to medium high and bring to a boil, whisking frequently. Simmer until thick for about 5 minutes until thickened. Season with salt and pepper to taste.
  • Combine brussels sprouts mixture with the sauce and pour into the prepared casserole dish. Melt remaining 2 tablespoons of butter and combine with the breadcrumbs in a medium bowl. Add the french fried onions. Scatter mixture on top of the brussels sprouts mixture.
  • Bake casserole until bubbly and topping is brown, about 20-25 minutes.
Note: This casserole can be prepared ahead of time. Let baked casserole cool completely, then cover with plastic wrap and chill in the fridge for up to 2 days. To reheat, cover with foil and warm in a 350°F oven for about 30 minutes. Remove foil for the last 5-10 minute to get the topping nice and crispy again.


Calories: 356kcal, Carbohydrates: 27g, Protein: 6g, Fat: 26g, Saturated Fat: 14g, Cholesterol: 41mg, Sodium: 485mg, Potassium: 522mg, Fiber: 4g, Sugar: 3g, Vitamin A: 1161IU, Vitamin C: 73mg, Calcium: 91mg, Iron: 2mg
Have you tried this recipe?I’d love to hear about it! Leave a review below or take a photo and tag it on Instagram @completelydelicious with #completelydelicious.