If you’re looking for the ultimate comfort food side dish to wow your guests or just treat yourself, look no further than this Cheesy Mushroom and Onion Green Bean Casserole Recipe. Imagine tender green beans smothered in a creamy, cheesy sauce bursting with umami-rich mushrooms and sweet caramelized onions, all crowned with a blanket of crispy fried onions. Every spoonful delivers a perfect mix of textures and flavors—rich, savory, and positively irresistible, whether it’s a holiday feast or a weeknight dinner at home.
Ingredients You’ll Need
The beauty of this Cheesy Mushroom and Onion Green Bean Casserole Recipe lies in its straightforward, wholesome ingredients—each one playing a critical role in building depth, creaminess, and that craveable golden crunch on top. Here’s what you’ll gather for your casserole adventure:
- Fresh Green Beans: Trimmed and cut into 2-inch pieces, these provide a snappy, vibrant base that soaks up all the saucy goodness.
- Butter: Adds richness and helps to caramelize the onions for a sweet, savory bite.
- Olive Oil: Prevents the butter from burning and gives veggies an extra layer of flavor.
- Yellow Onion: When sliced and slowly cooked, onion brings a sweet, complex savoriness that elevates the casserole.
- Cremini or Button Mushrooms: Sliced mushrooms contribute a meaty texture and earthy flavor.
- Garlic Cloves: Just two cloves, minced, are enough to infuse the sauce with aromatic warmth.
- All-Purpose Flour: The flour thickens your cheesy sauce to the perfect creamy consistency.
- Whole Milk: Offers a silky base for the sauce without overwhelming richness.
- Heavy Cream: A splash of this lifts the sauce to luxurious, velvety heights.
- Salt: Essential to bring all the flavors into balance—don’t skip it!
- Black Pepper: Adds gentle zing and bite, enhancing every cheesy forkful.
- Garlic Powder: For a pop of extra garlicky flavor that weaves throughout the casserole.
- Shredded Sharp Cheddar Cheese: This is what transforms the dish from tasty to totally memorable—cheesy, melty, and bold.
- Grated Parmesan Cheese: Adds a salty, nutty kick to the top layer and helps everything turn beautifully golden.
- Crispy Fried Onions: The finishing touch—crunchy, salty, and completely addictive.
How to Make Cheesy Mushroom and Onion Green Bean Casserole Recipe
Step 1: Blanch the Green Beans
Start by preheating your oven to 375°F (190°C) and getting a large pot of salted water boiling. Drop in the trimmed green beans and let them cook for 4–5 minutes, just until they’re bright green and slightly tender. Drain them quickly and give them a cold rinse—this cools them down and locks in their vibrant color, so they’ll taste as fresh as they look in your Cheesy Mushroom and Onion Green Bean Casserole Recipe.
Step 2: Caramelize the Onions
Set a large skillet over medium heat, and melt the butter with a splash of olive oil. Add the sliced onions and let them gently cook down for about 10 to 12 minutes. Stir occasionally so they turn soft and golden—not burnt! Caramelized onions give the casserole a touch of sweetness and depth that makes every bite special.
Step 3: Sauté Mushrooms and Garlic
Once your onions are golden, scatter in the sliced mushrooms. Cook these for another 5 minutes, stirring so they get brown and tender, soaking up all that savory goodness. After the mushrooms are soft, toss in your minced garlic, letting it cook for just a minute, until fragrant. This trio is the flavor backbone of your Cheesy Mushroom and Onion Green Bean Casserole Recipe.
Step 4: Make the Creamy Sauce
Sprinkle the flour over your onion-mushroom mixture and stir to evenly coat everything. Gradually pour in the milk and heavy cream while stirring—this keeps lumps away. Cook the mixture for 2 to 3 minutes until it thickens up into a rich, dreamy sauce. Season with salt, black pepper, and a dash of garlic powder to layer in flavors.
Step 5: Melt in the Cheeses and Add Beans
With the skillet off the heat, stir in the shredded cheddar cheese. Watch it melt into the sauce, turning everything creamy and yellow. Gently fold in your blanched green beans, making sure each bean is coated in cheesy goodness. This gooey mixture is the heart of your Cheesy Mushroom and Onion Green Bean Casserole Recipe.
Step 6: Assemble and Bake
Grease a 9×13-inch baking dish and spread the cheesy bean mixture evenly inside. Sprinkle grated Parmesan over the top, then pile on the crispy fried onions (if you want extra crunch, save some onions for the final minutes of baking). Slide the dish into the oven and bake for 20–25 minutes until it’s bubbling and golden—exactly what you want for a showstopping casserole.
How to Serve Cheesy Mushroom and Onion Green Bean Casserole Recipe
Garnishes
Don’t underestimate the power of a fresh garnish! A sprinkle of extra crispy fried onions just before serving instantly perks up the casserole’s appearance and crunch. For a pop of color, add a scattering of chopped fresh parsley or chives—it lifts the entire dish. Even a dash more grated Parmesan just as it comes out of the oven can dial up the flavor and make every serving extra appealing.
Side Dishes
This Cheesy Mushroom and Onion Green Bean Casserole Recipe is incredibly versatile, playing well with all kinds of mains. It balances hearty roasts like turkey, chicken, or beef, and shines alongside other classic sides like mashed potatoes or stuffing. For weeknights, it complements a simple grilled protein or even a meatloaf beautifully. Its creamy richness makes it a hero dish at both holiday spreads and casual family dinners.
Creative Ways to Present
If you want to add a little flair, try baking individual portions of the casserole in small ramekins for a dinner party—it’s adorable and makes everyone feel special! For potlucks, use a pretty ceramic baking dish for easy transport and a touch of rustic charm. You can even arrange a handful of sautéed mushrooms or a sprinkle of green onions on top to hint at all the goodies inside your Cheesy Mushroom and Onion Green Bean Casserole Recipe.
Make Ahead and Storage
Storing Leftovers
Leftover Cheesy Mushroom and Onion Green Bean Casserole Recipe stores deliciously in the refrigerator. Just cover the baking dish tightly with foil or transfer to an airtight container. It will stay fresh for up to three days, and the flavors might even deepen as it sits—a win for next-day leftovers!
Freezing
If you’ve made too much (is there such a thing?), you can absolutely freeze this casserole before baking. Assemble everything except the crispy topping, wrap well with plastic and foil, and freeze for up to two months. When you’re ready, bake straight from the freezer (add extra time), topping with fried onions in the last few minutes for ultimate crunch.
Reheating
For best results, reheat leftover casserole in the oven at 350°F until warmed through and bubbling—this keeps the texture closer to fresh-baked. A quick blast under the broiler can refresh the fried onion topping to crisp perfection. You can also reheat individual portions in the microwave, though the topping will be a little softer.
FAQs
Can I use canned green beans instead of fresh?
While fresh green beans provide the best texture and color, canned green beans will work in a pinch—just rinse and drain them well. Note that the final dish may be a bit softer and less vibrant, but it will still taste delicious.
What can I substitute for cheddar cheese?
If you want to play with flavors, swap out cheddar for Gruyère or mozzarella, or try a blend! Gruyère adds nuttiness, while mozzarella brings gooey meltiness. Any good melting cheese will work in this Cheesy Mushroom and Onion Green Bean Casserole Recipe.
Can I make the casserole in advance?
Absolutely! You can assemble the casserole a day ahead, cover it tightly, and refrigerate. When you’re ready to bake, simply add the fried onions on top and pop it right in the oven. This makes hosting during the holidays or busy weekdays way less stressful.
Is there a way to make this recipe gluten-free?
Yes! Just substitute the all-purpose flour with a gluten-free flour blend, and use certified gluten-free crispy fried onions. The result will be just as creamy and satisfying as the original Cheesy Mushroom and Onion Green Bean Casserole Recipe.
How do I make the topping extra crispy?
For the crunchiest fried onion topping, add most of the onions in the last 10 minutes of baking rather than at the start. You can even mix in some panko breadcrumbs or extra Parmesan for additional texture and flavor.
Final Thoughts
I promise, once you try this Cheesy Mushroom and Onion Green Bean Casserole Recipe, it’ll become your new go-to for both special occasions and everyday dinners. The creamy sauce, golden cheese, and irresistibly crunchy topping truly make it an unforgettable side. Grab those green beans and let’s make comfort food memories together—your tastebuds will thank you!
Print
Cheesy Mushroom and Onion Green Bean Casserole Recipe
- Total Time: 50 minutes
- Yield: 8 servings 1x
- Diet: Vegetarian
Description
This Cheesy Mushroom and Onion Green Bean Casserole Recipe is a delicious twist on the classic green bean casserole. Creamy, cheesy, and packed with savory flavors, this vegetarian side dish is perfect for any occasion.
Ingredients
For the Green Beans:
- 1 1/2 pounds fresh green beans (trimmed and cut into 2-inch pieces)
For the Mushroom and Onion Mixture:
- 2 tablespoons butter
- 1 tablespoon olive oil
- 1 medium yellow onion (thinly sliced)
- 8 ounces cremini or button mushrooms (sliced)
- 2 garlic cloves (minced)
- 2 tablespoons all-purpose flour
- 1 cup whole milk
- 1/2 cup heavy cream
Seasonings and Cheeses:
- 1 teaspoon salt
- 1/2 teaspoon black pepper
- 1/2 teaspoon garlic powder
- 1 1/2 cups shredded sharp cheddar cheese
- 1/2 cup grated Parmesan cheese
For the Topping:
- 1 1/2 cups crispy fried onions
Instructions
- Preheat the oven: Preheat the oven to 375°F (190°C).
- Blanch the green beans: Bring a large pot of salted water to a boil and blanch the green beans for 4–5 minutes until just tender. Drain and rinse with cold water to stop cooking.
- Sauté the onions and mushrooms: In a large skillet, heat butter and olive oil over medium heat. Add the onions and sauté until golden and caramelized. Add mushrooms and cook until tender and browned. Stir in garlic.
- Make the sauce: Sprinkle flour over the mixture and stir to coat. Slowly add milk and cream while stirring, then cook until thickened. Stir in salt, pepper, garlic powder, and cheddar cheese until melted.
- Combine and bake: Remove from heat and fold in the green beans. Pour the mixture into a greased 9×13-inch baking dish. Top with Parmesan and crispy fried onions. Bake for 20–25 minutes, or until bubbly and golden on top.
Notes
- You can make the casserole a day ahead and refrigerate before baking.
- Swap cheddar for Gruyère or mozzarella for a flavor variation.
- For extra crisp topping, add fried onions in the last 10 minutes of baking.
- Prep Time: 25 minutes
- Cook Time: 25 minutes
- Category: Side Dish
- Method: Baking
- Cuisine: American
Nutrition
- Serving Size: 1 portion
- Calories: 280
- Sugar: 5g
- Sodium: 470mg
- Fat: 19g
- Saturated Fat: 10g
- Unsaturated Fat: 7g
- Trans Fat: 0g
- Carbohydrates: 17g
- Fiber: 3g
- Protein: 8g
- Cholesterol: 40mg
