Creamy Mushroom Green Bean Casserole with Crispy Onions Recipe

If you’re on the hunt for the ultimate comfort side dish that feels both classic and fresh, you’re in for a treat with my Creamy Mushroom Green Bean Casserole with Crispy Onions Recipe. I absolutely love how this updated version takes the humble green bean casserole to a whole new level with fresh mushrooms, a luscious homemade cream sauce, and those irresistible crispy onions on top. Trust me, once you try this, it might just become your new holiday staple or weeknight favorite!

this Recipe

Ingredients You’ll Need

I love how these ingredients come together for a comforting dish that’s full of umami and texture. When shopping, look for firm, vibrant green beans and meaty cremini mushrooms—they really make a difference!

• Green Beans: Fresh and crisp green beans are key—they blanch beautifully and keep their bite.
• Extra-Virgin Olive Oil: Adds richness and helps soften the mushrooms without overpowering them.
• Cremini Mushrooms: Their earthy flavor is essential to the creamy sauce and gives depth.
• Tamari: This gluten-free soy sauce alternative adds savory complexity to the mushrooms.
• Garlic: Freshly minced for that fragrant punch without being too sharp.
• Fresh Thyme Leaves: Aromatic herbs like thyme brighten up the creamy sauce nicely.
• All-Purpose Flour: Used to thicken the sauce, giving it that luscious texture.
• Milk: You can use any kind you prefer—whole milk makes the sauce richer, but I’ve found others work just fine.
• Dijon Mustard: Just a touch enhances the flavor without making it tangy.
• Parmesan Cheese: Adds a subtle nutty saltiness that perfectly rounds out the creamy sauce.
• Freshly Ground Black Pepper: For seasoning and a little spice.
• French Fried Onions: Store-bought is convenient, but I love making crispy baked onions for extra freshness.

Variations

I like to mix things up depending on the season or occasion. Feel free to customize this creamy mushroom green bean casserole with crispy onions recipe to your taste—you’ll be amazed how versatile it is!

• Vegetarian Variation: Use vegetable broth instead of tamari or add a splash of soy sauce to keep it umami-rich without animal products.
• Make it Vegan: Swap milk for unsweetened almond or oat milk, and use nutritional yeast in place of Parmesan—I’ve tried it, and it’s surprisingly delicious!
• Extra Crunch: Add toasted sliced almonds or pecans on top along with the onions for a nutty twist, which my family goes crazy for.
• Seasonal Twist: Swap thyme with rosemary or sage during the holidays for a different herbal note.

How to Make Creamy Mushroom Green Bean Casserole with Crispy Onions Recipe

Step 1: Prep Your Green Beans Like a Pro

Start by trimming and halving your green beans. Bring a big pot of salted water to a boil—then blanch your green beans for exactly 4 minutes. This locks in their vibrant color and gives them that perfect tender-crisp texture. Don’t skip the ice bath afterward; plunging them into ice water stops the cooking right away and keeps them from turning mushy. Pat them dry on a towel once they’ve cooled so they don’t water down your sauce later.

Step 2: Cook Your Mushrooms into Creamy Perfection

Heat extra-virgin olive oil in a large skillet over medium heat. Toss in those lovely sliced cremini mushrooms and cook them down until they’re soft and golden, about 8 to 10 minutes. Add tamari, garlic, and fresh thyme—this combo is what makes the sauce pop with flavor. Then sprinkle the flour over the mushroom mixture and stir well to create a roux. Slowly pour in the milk and Dijon mustard, whisking constantly so you don’t end up with lumps. Let this simmer gently until thickened, about 15 to 20 minutes—this patience pays off! Stir in the grated Parmesan and freshly ground pepper, then take it off the heat.

Step 3: Assemble and Bake to Golden Goodness

Spread a third of the creamy mushroom sauce into your prepared 9×13-inch baking dish. Layer the blanched green beans over the sauce, then pour the remaining sauce on top. Finally, blanket the whole casserole with crispy French fried onions or your homemade crispy baked onions. Cover the dish and bake at 400°F for 10 minutes, then uncover and bake for another 10 minutes until bubbling and golden on top. Keep an eye on those onions because they can brown fast—if they start getting dark too soon, simply cover the dish to finish baking. For an extra touch, sprinkle a little more Parmesan cheese right before serving.

How to Serve Creamy Mushroom Green Bean Casserole with Crispy Onions Recipe

Garnishes

I usually finish this casserole with a sprinkle of extra Parmesan cheese for a little salty tang. Sometimes I add a few fresh thyme sprigs on top for a pop of color and fresh aroma. A squeeze of fresh lemon juice right before serving can also brighten all those rich flavors if you’re feeling adventurous!

Side Dishes

This casserole pairs beautifully with roasted turkey or baked chicken for a classic dinner. If you’re hosting a casual meal, mashed potatoes or garlic bread make excellent companions. For lighter fare, a crisp green salad provides a refreshing contrast to the richness of the green bean casserole.

Creative Ways to Present

For special occasions, I like to serve the casserole in individual ramekins topped with mini crispy onion nests. It makes the presentation feel festive and elegant. Sometimes, I make it in a cast-iron skillet right on the table for a rustic vibe that’s perfect for cozy dinners.

Make Ahead and Storage

Storing Leftovers

I usually store leftovers covered tightly in the fridge for up to 3 days. The casserole is fantastic reheated—the sauce keeps its creaminess and the onions stay fairly crisp if you add a few fresh crispy onions when reheating.

Freezing

Freezing cream-based casseroles can be tricky, but I’ve found it works best if you freeze the casserole before baking. Wrap tightly in foil or plastic wrap, then thaw overnight in the fridge before baking as usual. The onions are best added fresh after baking to maintain crunch.

Reheating

To reheat, cover the casserole loosely with foil and warm in a 350°F oven until heated through—about 20 minutes. To restore some crispness, sprinkle on extra crispy onions and pop it under the broiler for a minute or two.

FAQs

Final Thoughts

This Creamy Mushroom Green Bean Casserole with Crispy Onions Recipe holds a special place in my kitchen because it combines comfort and freshness in one dish. Every time I serve it, I’m reminded how simple ingredients can create something truly unforgettable — and how a little extra love, like those homemade crispy onions, makes all the difference. I can’t wait for you to try it and hear how it becomes a beloved favorite in your home too!

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