If you’re craving a fresh twist on classic comfort food, you’re going to absolutely fall in love with this Creamy Mushroom and Green Bean Casserole with Crispy Onions Recipe. It’s that perfect cozy dish that’s creamy, packed with savory mushrooms and tender green beans, and topped with irresistibly crispy onions that keep everyone coming back for more. Trust me, once you try this, it’ll become a go-to for family dinners and holiday spreads alike.
Why You’ll Love This Recipe
- Fresh and Flavorful: Unlike store-bought casseroles, this recipe uses fresh green beans and mushrooms for a vibrant taste.
- Creamy Comfort: The homemade mushroom sauce is rich and velvety, making every bite feel indulgent but not heavy.
- Crispy Onion Topping: The combination of crispy onions on top adds the perfect crunch and texture contrast.
- Great for Any Occasion: Whether weeknight dinner or holiday side, this casserole impresses without stress.
Ingredients You’ll Need
This dish comes together with simple, wholesome ingredients you might already have, plus a few fresh pantry staples. I love how the flavors meld beautifully — earthy mushrooms, fresh thyme, and sharp Parmesan all soaking into green beans. If you can, try to get cremini mushrooms for a deeper flavor, but white button mushrooms work fine too.
- Green Beans: Fresh and crisp beans make the difference here; I always trim and cut them just right for easy eating.
- Extra-Virgin Olive Oil: Adds richness to sautéed mushrooms without overpowering.
- Cremini Mushrooms: They have a nice meaty flavor and hold up well during cooking.
- Tamari: I prefer tamari for its deeper umami and gluten-free bonus, but soy sauce works too.
- Garlic: Fresh minced garlic gives that punch of aromatic flavor.
- Fresh Thyme Leaves: A lovely herbal touch that pairs perfectly with mushrooms.
- All-Purpose Flour: Helps thicken the sauce; don’t skip this step to get that creamy texture.
- Milk: Use any kind you like; whole milk gives the creamiest result, but I’ve tried almond milk for a dairy-free tweak.
- Dijon Mustard: Adds a subtle tang and brightness to the sauce.
- Parmesan Cheese: Grated fresh is best—it melts smoothly and adds a savory depth.
- Freshly Ground Black Pepper: Just enough spice to balance the creaminess.
- French Fried Onions: The crowning glory—crispy, crunchy topping that seals the deal.
Variations
I love that this recipe is flexible — you can easily tweak it to suit what you have on hand or your personal taste. Over the years, I’ve tried switching out ingredients, and I encourage you to make it your own!
- Mushroom Mix: Once, I swapped cremini for shiitake and portobello mushrooms — the earthiness was next-level delicious!
- Dairy-Free Version: Using a plant-based milk like oat or almond and nutritional yeast instead of Parmesan works beautifully.
- Crispy Onion Alternatives: Homemade baked crispy onions are my secret for a fresher topping, especially when I avoid store-bought.
- Add Crunch: Toasted almonds or pecans sprinkled on top add a nice unexpected crunch for a twist.
How to Make Creamy Mushroom and Green Bean Casserole with Crispy Onions Recipe
Step 1: Blanch the Green Beans to Tender-Crisp Perfection
Fill a large pot with salted water and bring it to a rolling boil. Add your trimmed and halved green beans and blanch them for about 4 minutes — you want them tender but still with a little snap. Remove them promptly and plunge into an ice water bath to stop the cooking process. This technique keeps their vibrant color and prevents mushiness. After cooling, drain and pat them dry with a clean kitchen towel. I learned the hard way that skipping the ice bath yields soggy beans, so don’t skip this step!
Step 2: Sauté Mushrooms for Deep Flavor
Heat your extra-virgin olive oil in a large skillet over medium-high heat. Add sliced cremini mushrooms and cook for 8–10 minutes until they release their moisture and begin to brown. Then, stir in tamari, minced garlic, and fresh thyme leaves — this combo infuses such aromatics into the mushrooms. Make sure to keep stirring so nothing sticks or burns. Your kitchen will smell incredible at this point!
Step 3: Make the Creamy Mushroom Sauce
Sprinkle the all-purpose flour evenly over the mushrooms; stirring, let it cook for another minute to cook off the raw flour taste. Gradually whisk in the milk and Dijon mustard. Keep cooking and whisking frequently for about 15–20 minutes until the sauce thickens up and coats the back of your spoon. Stir in the grated Parmesan cheese and freshly ground pepper. You’ll see the sauce transform—thick, luscious, and packed with umami — I absolutely love this stage!
Step 4: Assemble and Bake
Preheat your oven to 400°F and lightly grease a 9×13-inch baking dish. Spread one-third of the creamy mushroom sauce on the bottom, layer with the blanched green beans, then pour the remaining sauce evenly over the top. Finish by sprinkling the French fried onions or your own crispy baked onions generously on top. Cover the dish and bake for 10 minutes, then uncover and bake for another 10 minutes until bubbly and golden. If the onions brown too fast, tent the dish with foil. Once out of the oven, sprinkle with extra Parmesan if you want to go all out.
Pro Tips for Making Creamy Mushroom and Green Bean Casserole with Crispy Onions Recipe
- Don’t Skip the Ice Bath: Blanching then shocking the beans locks in color and crunch, which truly elevates this casserole.
- Use Fresh Thyme: Dried herbs don’t provide the same brightness; fresh thyme lifts the whole flavor profile beautifully.
- Whisk Constantly When Thickening: Prevents lumps and ensures a smooth, creamy sauce every time.
- Cover During Baking If Needed: Protects crispy onions from burning while letting everything else cook perfectly.
How to Serve Creamy Mushroom and Green Bean Casserole with Crispy Onions Recipe
Garnishes
I like to keep garnishes simple: a sprinkle of extra Parmesan over the top right out of the oven adds a lovely salty finish and some fresh thyme sprigs for a pop of color. Sometimes I add a few toasted almond slices for crunch variation — it’s a nice surprise that friends ask about every time!
Side Dishes
This casserole pairs wonderfully with roasted chicken or turkey, making it a terrific holiday side dish. It also goes great alongside creamy mashed potatoes or a simple quinoa salad for a full meal. One of my favorite combos is with lemon herb grilled salmon — the creaminess balances the bright, zesty fish perfectly.
Creative Ways to Present
For special occasions, I’ve baked individual portions in ramekins topped with a small nest of crispy onions and a sprig of thyme. It looks elegant but is extra cozy. Another time, I layered it in a trifle dish for a family-style buffet — everyone loved scooping out their own portions with the perfect ratio of sauce, beans, and onions.
Make Ahead and Storage
Storing Leftovers
I store leftover casserole in an airtight container in the fridge. It stays great for 3-4 days and the flavors actually deepen overnight, which can be a real bonus for busy weeknights.
Freezing
I’ve frozen this casserole successfully by baking it first, then letting it cool, and wrapping it tightly with foil and plastic wrap before freezing. When you want to enjoy it again, thaw overnight in the fridge and reheat in the oven to keep the crispy onions from getting soggy.
Reheating
Reheat leftovers in a 350°F oven for about 15–20 minutes. To revive crispy onions, sprinkle a little fresh topping before reheating or pop the casserole under the broiler for a minute—but watch carefully to avoid burning.
FAQs
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Can I use frozen green beans for this casserole?
Yes, you can—but fresh green beans yield a better texture and taste. If using frozen, thaw and drain them well, then sauté briefly before assembling to avoid excess water causing a soggy casserole.
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Can I make the creamy mushroom sauce ahead of time?
Absolutely. You can prepare the sauce a day ahead and store it covered in the fridge. Rewarm gently on the stove, whisking to smooth it out, before assembling the casserole.
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What can I use instead of French fried onions?
If you don’t have French fried onions, making your own crispy baked onions is a great alternative. You can thinly slice onions, toss them with a little flour and seasoning, then bake until crisp. They add freshness and control on saltiness.
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Is this casserole gluten-free?
Not as written because of the flour and tamari (unless you use gluten-free tamari and substitute the flour with a gluten-free alternative like cornstarch). Making these swaps allows you to enjoy this casserole gluten-free without compromising taste.
Final Thoughts
This Creamy Mushroom and Green Bean Casserole with Crispy Onions Recipe holds a special place in my kitchen because it combines all the best comfort food qualities: it’s creamy, hearty, and refreshingly fresh thanks to those green beans. When I first made it, the whole family went crazy — it’s now a tradition at every holiday and even a regular weeknight favorite. I can’t recommend it enough if you want to impress without stress. Give it a go and let me know how it becomes a staple in your home too!
Print
Creamy Mushroom and Green Bean Casserole with Crispy Onions Recipe
- Prep Time: 20 minutes
- Cook Time: 60 minutes
- Total Time: 80 minutes
- Yield: 8 servings
- Category: Side Dish
- Method: Baking
- Cuisine: American
- Diet: Vegetarian
Description
A modern twist on the traditional green bean casserole featuring fresh green beans, a creamy homemade mushroom sauce, and topped with crispy fried onions. This comforting side dish is perfect for holiday meals and family gatherings.
Ingredients
Vegetables
- 1½ pounds green beans (trimmed and halved)
- 16 ounces cremini mushrooms (sliced)
- 4 garlic cloves (minced)
- 2 tablespoons fresh thyme leaves
Sauce
- 2 tablespoons extra-virgin olive oil
- 2 tablespoons tamari
- ¼ cup all-purpose flour
- 3 cups milk (any kind)
- 1½ teaspoons Dijon mustard
- ½ cup grated Parmesan cheese (plus more for sprinkling)
- ¼ teaspoon freshly ground black pepper
Topping
- 1½ cups French fried onions (or homemade Crispy Baked Onions, see recipe notes)
Instructions
- Preheat and prepare baking dish. Preheat the oven to 400°F (204°C) and lightly grease a 9×13-inch baking dish to prevent sticking.
- Blanch green beans. Bring a large pot of salted water to a boil. Drop in the trimmed and halved green beans and blanch for 4 minutes. Quickly drain and immerse them in a bowl of ice water to stop the cooking process, then drain again and pat dry with a towel.
- Cook mushrooms. Heat olive oil in a large skillet over medium heat. Add the sliced cremini mushrooms and cook until softened, about 8 to 10 minutes. Stir in tamari, minced garlic, and fresh thyme leaves.
- Make the sauce. Sprinkle the flour over the mushroom mixture and stir to coat. Gradually add the milk and Dijon mustard, stirring constantly to combine. Simmer the sauce until thickened, about 15 to 20 minutes, whisking often to avoid lumps. Once thickened, stir in the grated Parmesan cheese and freshly ground black pepper.
- Assemble casserole. Spread one-third of the mushroom sauce evenly in the prepared baking dish. Layer the blanched green beans over the sauce, then top with the remaining mushroom sauce, spreading to cover the beans.
- Add topping and bake. Sprinkle the French fried onions evenly over the top of the casserole. Cover the dish with foil and bake for 10 minutes. Remove the foil and bake uncovered for an additional 10 minutes. If the onions brown too quickly, re-cover the dish to prevent burning.
- Garnish and serve. Optionally sprinkle a little more grated Parmesan cheese on top before serving. Serve hot as a delicious side dish.
Notes
- This recipe updates the classic green bean casserole by using fresh green beans and a homemade mushroom sauce instead of canned soup, making it healthier and more flavorful.
- French fried onions add a delightful crunch, but you can substitute with homemade crispy baked onions for a fresher alternative.
- If using homemade onions, ensure they are baked until golden and crispy before adding to the casserole.
- Be careful to avoid over-browning the onions during baking by covering the casserole if necessary.
Nutrition
- Serving Size: 1 cup
- Calories: 220
- Sugar: 4g
- Sodium: 350mg
- Fat: 10g
- Saturated Fat: 3g
- Unsaturated Fat: 6g
- Trans Fat: 0g
- Carbohydrates: 22g
- Fiber: 4g
- Protein: 8g
- Cholesterol: 15mg
