This Mushroom green bean casserole is the ultimate homemade comfort food, crafted from fresh green beans and savory cremini mushrooms in a rich, creamy sauce. It comes together in about an hour and a half, making it an ideal, beloved side dish for holiday feasts and cozy family dinners alike.

This classic green bean mushroom bake holds a special place at my family’s table, especially during the holidays. I love how its earthy aroma fills the kitchen, a scent that instantly signals warmth and celebration. It has become our go-to traditional Thanksgiving casserole, perfectly complementing the rich flavors of our main courses like a classic roast turkey or a comforting chicken pot pie. For a truly spectacular spread, I love to serve it alongside other favorites, such as my creamy sweet potato casserole.

Everything for Your Perfect Mushroom Green Bean Casserole

Be sure to see the recipe card below for the full listing of ingredients, instructions, notes, and estimated nutritional information.

Mushroom Green Bean Casserole

Make this classic mushroom green bean casserole from scratch with fresh ingredients. Perfect for holidays or family dinners with creamy sauce and crispy onions.

Print Recipe Pin Recipe

Prep Time 25 minutes mins

Cook Time 1 hour hr

Total Time 1 hour hr 25 minutes mins

Course Dinner

Cuisine American

Servings 6 servings

Calories 320 kcal

Equipment

• oven
• large pot
• Dutch oven or oven-safe skillet
• cutting board
• knife
• measuring cups
• measuring spoons
• whisk
• mixing bowl
• 9×13-inch baking dish

Ingredients

  

Main Ingredients

• 1.5 pounds fresh green beans trimmed
• 4 tbsp unsalted butter
• 1 pound cremini mushrooms sliced
• 1 medium yellow onion finely chopped
• 2 cloves garlic minced
• 0.25 cup all-purpose flour
• 2 cups low-sodium chicken or vegetable broth
• 1 cup whole milk
• 0.5 cup heavy cream
• 1 tsp Dijon mustard
• 1 tsp fresh thyme leaves chopped
• 1 tsp kosher salt or to taste
• 0.5 tsp freshly ground black pepper or to taste
• 1 can crispy fried onions 2.8-ounce can, divided

Instructions

 

• Preheat your oven to 375 degrees Fahrenheit. If using fresh green beans, bring a large pot of salted water to a rolling boil. Add the trimmed green beans and cook for 5 to 7 minutes, or until they are crisp-tender and vibrant green. Drain immediately and plunge them into an ice bath to stop the cooking, then drain thoroughly and set aside. If using frozen green beans, thaw them completely and pat them dry.
• Melt the unsalted butter in a large Dutch oven or a deep, oven-safe skillet over medium-high heat. Add the sliced cremini mushrooms and cook, stirring occasionally, for 8 to 10 minutes, until they release their moisture, brown nicely, and are tender. Remove the mushrooms from the pan and set them aside.
• Reduce the heat to medium. Add the finely chopped yellow onion to the same pan and cook, stirring frequently, for 5 to 7 minutes, until it softens and becomes translucent. Stir in the minced garlic and cook for another 1 minute, until fragrant, being careful not to let it brown.
• Sprinkle the all-purpose flour over the onion and garlic mixture, stirring constantly for 1 minute to create a roux. Gradually whisk in the low-sodium chicken or vegetable broth, then the whole milk, and finally the heavy cream, ensuring there are no lumps. Bring the sauce to a gentle simmer, stirring constantly, and cook for 3 to 5 minutes, or until it has thickened enough to coat the back of a spoon. Stir in the Dijon mustard, chopped fresh thyme, kosher salt, and freshly ground black pepper. Taste and adjust seasonings as needed.
• Return the cooked mushrooms and the prepared green beans to the sauce in the skillet or Dutch oven. Stir gently to ensure all the green beans are evenly coated. If your skillet is not oven-safe, transfer the mixture to a 9×13-inch baking dish.
• Bake the casserole in the preheated oven for 20 to 25 minutes, or until the sauce is bubbly around the edges and the top is lightly golden.
• Remove the casserole from the oven. Sprinkle 1 1/2 cups of the crispy fried onions evenly over the top. Return the casserole to the oven and bake for an additional 5 minutes, or until the crispy fried onions are golden brown and warmed through.
• Let the casserole rest for 5 to 10 minutes before serving. This allows the sauce to set slightly, making it easier to serve.

Notes

Let the casserole rest for 5-10 minutes before serving to allow the sauce to set slightly.

Keyword casserole, green beans, holiday, mushrooms

Ways to Customize This Casserole

• Make It Cheesier: Stir a cup of shredded sharp cheddar or Gruyère into the sauce before baking.
• Add Protein: For a heartier main dish, add two cups of diced, cooked chicken or turkey.
• Gluten-Free Version: Simply use a 1:1 gluten-free flour blend to make the roux.

My Tips for Casserole Perfection

• Blanch for Vibrant Color: Shocking the green beans in ice water stops the cooking process, locking in that beautiful green hue.
• Brown the Mushrooms Deeply: Let the mushrooms develop a rich, golden-brown color for the best savory flavor in your creamy mushroom casserole.
• Achieve the Perfect Roux: Cook the flour with the butter and onions for a full minute to avoid a raw flour taste in your sauce.
• Let It Rest Before Serving: Allowing the casserole to sit for 5-10 minutes lets the sauce thicken for cleaner slices, just like when you make a perfect breakfast casserole.

How to Store and Reheat Your Casserole

• Store: Cool completely, then transfer to an airtight container. It will keep in the refrigerator for up to 4 days.
• Freeze: Freeze individual portions or the entire baked casserole in a freezer-safe container for up to 3 months. Thaw in the refrigerator overnight before reheating.
• Reheat: Cover with foil and warm in a 350°F oven for 15-20 minutes, or until heated through. Add fresh crispy onions after reheating.
• Make-Ahead Tip: You can assemble the entire casserole (without the onion topping) a day ahead, cover, and refrigerate. Bake as directed, adding 5-10 minutes to the initial baking time.

Frequently Asked Questions

More Comforting Casserole Recipes

• Corn Casserole
• Southern Sweet Potato Casserole
• Creamy Mac and Cheese
• Beef Stew
• Cottage Pie
• Sheet Pan Lasagna

Make This Mushroom Green Bean Casserole Tonight

With its creamy sauce, tender vegetables, and irresistible crispy topping, this homemade Mushroom green bean casserole is sure to become a new family favorite. It brings a touch of homemade elegance to any meal, from a simple weeknight dinner to your most cherished holiday gatherings. I hope it brings as much comfort and joy to your table as it has to mine.