Side Dishes
America's Test Kitchen's green bean casserole delivers the iconic crispy fried onion topping and velvety mushroom sauce without the usual greasy mess. The secret lies in precise layering and oven techniques that create a perfectly textured dish every time.
After years of testing, this method guarantees restaurant-quality results with just 30 minutes of active prep and 30 minutes baking.
What sets this recipe apart is the creamy mushroom sauce made from scratch—no canned soup here. Sautéed onions and mushrooms form the flavor base, then blended with cream and a touch of mustard for depth.
The sauce gets thickened just right so it doesn't turn watery during baking, while the fried onions get crisped separately for maximum crunch.
By the time it emerges from the oven, you'll have golden-brown fried onions forming a crispy lattice on top of tender green beans swimming in that rich, creamy mushroom sauce. The texture contrast is what makes this dish legendary—crunchy, cheesy, and perfectly balanced in every bite.
This version scales beautifully for holidays or weeknight dinners, and the prep can be done ahead. The key is maintaining the right oven temperature and baking time to ensure the top stays crispy while the sauce remains creamy. Here's everything you need to make it perfectly.
Ingredients for america's test kitchen green bean casserole
The essential ingredients for America's Test Kitchen's legendary green bean casserole—crispy, creamy, and perfectly balanced.
| Ingredient | Amount | Notes |
|---|---|---|
| Fresh Green Beans 🥦 | 1 ½ lb | Trimmed, cut into 2-inch pieces |
| Yellow Onions 🧅 | 1 whole | Medium, diced for sauce and frying |
| White Onions 🧅 | 1 whole | Medium, thinly sliced for frying |
| Mushrooms 🍄 | 8 oz | Cremini or white, sliced |
| Heavy Cream 🥛 | 1 cup | Full-fat for richness |
| Dijon Mustard 🍯 | 1 tbsp | For depth of flavor |
| All-Purpose Flour 🌾 | 1 tbsp | For sauce thickening |
| Shredded Cheddar Cheese 🧀 | 1 cup | Medium sharp variety |
| Unsalted Butter 🧈 | 4 tbsp | Cold for frying onions |
| Salt 🧂 | 1 ½ tsp | Kosher or sea salt |
| Black Pepper 🌶️ | ½ tsp | Freshly ground preferred |
| Garlic Cloves 🧄 | 3 cloves | Minced for sauce |
| Fresh Parsley 🌿 | ¼ cup | Chopped for garnish |
The onions are the foundation—both for the sauce and the crispy topping. Yellow onions for the base add sweetness, while white onions fry up crispier. Grab the medium-sized ones from the grocery store's produce section—they're consistent and sweet. For the mushrooms, cremini or white work best—their meaty texture holds up during cooking. The heavy cream is non-negotiable here; light cream won't give you that velvety texture. If you're in a pinch, half-and-half will work, but it's noticeably lighter. The Dijon mustard is what gives the sauce that subtle tang—don't skip it.
No yellow onions? Red onions work in a pinch, but they'll add more color than sweetness. White onions too expensive? Shallots are a great swap—they're milder and sweeter. The mushrooms can be swapped for shiitake if you want an earthier flavor. For the cheese, Pepper Jack adds a nice kick, but stick with cheddar for classic flavor. The butter for frying should be cold and unsalted—this ensures maximum crispiness without adding extra salt. If you're worried about the onions burning, fry them in small batches so they cook evenly. The parsley is purely for garnish, but it adds that fresh pop of color that makes the dish look restaurant-worthy.
The fried onions will keep in an airtight container for up to 3 days, but they're best used fresh. The mushroom sauce can be made a day ahead and reheated gently—just add a splash of milk or cream to loosen it if needed. The whole casserole reheats beautifully, though the onions may lose a bit of their crunch. For best results, reheat covered at 350°F for 15-20 minutes. If you're making this ahead for a holiday gathering, assemble it the night before and refrigerate—it'll be even more flavorful the next day.
Why You'll Love This Recipe
- One-Pan Magic: I swear by this recipe when I’m too tired to wash dishes. The green beans, onions, and mushrooms all go into one skillet—no chopping chaos, no extra pots. Just sauté, simmer, and serve while the kitchen stays (mostly) clean.
- Creamy Crunch Perfection: That crispy fried onion topping with the velvety heavy cream sauce? It’s the kind of contrast that makes you close your eyes and sigh. The mushrooms add this earthy depth that turns a simple side into something you’d happily eat as a main.
- Holiday or Weeknight: Between us—this dish works everywhere. Slap it on the table for Thanksgiving when you’re overwhelmed, or reheat it for a lazy Tuesday when you’re craving something hearty. The flavors hold up, no matter the occasion.
- Budget-Friendly Leftovers: Fresh green beans and mushrooms might sound fancy, but they stretch this recipe into three meals without breaking the bank. The heavy cream makes it feel indulgent, but the onions keep costs low. Plus, it reheats like a dream—no sad, soggy sides here.
Step-by-step instructions for america's Test Kitchen green bean casserole
Here's how to build the perfect casserole with a golden, crispy topping and rich, velvety mushroom sauce.
Blanch and Prepare the Green Beans
Trim the ends from the 1.5 lb fresh green beans and cut them into 2-inch pieces. Spread them out on a baking sheet and steam in a microwave-safe bowl with 1 cup of water for 3 minutes. Drain immediately and plunge into ice water to stop cooking. This step ensures tender-crisp beans that won't turn mushy in the oven.
Drain well and transfer the cooled green beans to a large mixing bowl. Add the 1 cup shredded cheddar cheese and toss gently to coat. This pre-mixing prevents the cheese from clumping later and distributes it evenly throughout the casserole. Set aside while you prepare the onion mixture.
Fry the Onions for Crispy Texture
Cut the 1 whole yellow onion and 1 whole white onion into thin slices. Melt 2 tbsp of the unsalted butter in a large skillet over medium heat. Add half of the yellow and white onion slices and fry for 8-10 minutes, stirring occasionally, until golden brown and crisp. Remove with a slotted spoon and drain on paper towels.
In the same skillet, melt the remaining 2 tbsp unsalted butter. Add the remaining onion slices and fry for another 8-10 minutes until deeply golden. The onions should be crisp enough to hold their shape when transferred to paper towels. This two-batch approach prevents overcrowding and ensures maximum crispiness.
Make the Creamy Mushroom Sauce
In the same skillet with the crispy onions, add the 8 oz sliced mushrooms and cook for 5-6 minutes until they release their moisture and begin to brown. Stir in the 3 minced garlic cloves and cook for 30 seconds until fragrant. Remove from heat and transfer the mushroom mixture to a blender.
Add the 1 cup heavy cream, 1 tbsp Dijon mustard, and 1 tbsp all-purpose flour to the blender. Blend until completely smooth. Return the mixture to the skillet and cook over medium heat for 3-4 minutes, stirring constantly, until the sauce thickens enough to coat the back of a spoon. Season with 1 tsp salt and 0.25 tsp black pepper.
Assemble the Casserole
Preheat your oven to 375°F. In a 9x13-inch baking dish, spread half of the green bean and cheese mixture evenly. Pour half of the mushroom sauce over the beans, spreading it to cover completely. Top with half of the crispy fried onions. Repeat with the remaining green beans, sauce, and onions, finishing with a final layer of onions on top.
Bake uncovered for 25-30 minutes until the top is golden brown and bubbly. The edges should be crispy while the center remains creamy. If the top browns too quickly, tent loosely with foil for the last 10 minutes of baking. This ensures a perfect balance of crispy and creamy textures throughout.
Rest and Garnish
Remove from the oven and let the casserole rest for 10 minutes. This resting period allows the layers to set and the flavors to meld. Sprinkle the 0.25 cup chopped fresh parsley evenly over the top just before serving. The parsley adds a fresh contrast to the rich, creamy sauce and crispy onions.
Serve immediately while the top is still crispy and the sauce is warm. The casserole should have a perfect balance of textures - tender green beans, creamy mushroom sauce, and crispy fried onions on top. Each bite delivers all three elements together for maximum flavor and satisfaction.
Pro Tips For Making America'S Test Kitchen Green Bean Casserole
- Blanch Beans First: I learned this the hard way—raw green beans in a creamy sauce turn mushy. Blanch them for 3 minutes in boiling salted water, then shock in ice water before adding to the dish. This keeps them crisp-tender and holds their shape through baking.
- Sauté Onions Low and Slow: The recipe calls for onions, but I used to rush them and end up with bitter, browned bits. Cook them on medium-low heat for 10-12 minutes until fully translucent—no color, just soft. This builds flavor without overpowering the creamy sauce.
- Skip Pre-Cooked Mushrooms: Canned mushrooms add moisture but lose texture. Use fresh cremini or white mushrooms, sliced ¼-inch thick, and cook them until all their liquid evaporates. This prevents a watery sauce and keeps the casserole’s texture consistent.
- Whisk Cream Cold: Heavy cream straight from the fridge blends smoother and doesn’t curdle when mixed with warm onions. Stir it into the sauce off the heat—just until combined—and resist the urge to overmix. Lumps disappear faster this way.
Regional styles of this recipe
Classic Midwest Style
In the heartland, this casserole becomes a comforting centerpiece for holiday dinners. The key difference? A thicker mushroom sauce—I blend in 2 tbsp cornstarch with the flour to eliminate any wateriness during baking.
The onions get fried in lard instead of butter for extra crispiness, a nod to traditional Southern techniques. Serve with a side of buttered dinner rolls to soak up every last bit of sauce. 🧂
Southern Fried Twist
Down South, the casserole gets a spicy kick with ½ tsp cayenne pepper added to the sauce and a sprinkle of smoked paprika on the fried onions. I swap half the cheddar for sharp cheddar and add 1 chopped jalapeño to the sauce for heat.
The green beans stay tender-crisp, but the sauce gets a deeper, smoky character that pairs perfectly with collard greens on the side. 🌶️
Pacific Northwest Adaptation
On the West Coast, this dish becomes lighter with wild mushrooms (like chanterelles or morels) replacing cremini, and the sauce gets a boost of fresh thyme and lemon zest.
The onions are fried in avocado oil for a neutral flavor, and the dish is often served with grilled salmon or seared scallops as a protein pairing. The parsley garnish gets swapped for chopped chives to complement the earthy flavors. 🍄
New England Crispy Top
Up North, the focus is on an even crispier topping. I double the fried onions and press them into the sauce before baking to create a crust-like lattice.
The sauce gets a touch of white wine (about ¼ cup) for brightness, and the dish is finished with a sprinkle of grated Parmesan for umami depth. Serve with roasted Brussels sprouts or mashed potatoes for a hearty New England meal. ❄️
Tex-Mex Fusion
In Texas, the casserole gets a bold Southwest makeover. The sauce incorporates 1 tbsp chipotle powder and ½ cup salsa, while the onions are fried with 1 tsp cumin.
I swap the cheddar for Monterey Jack and top with crumbled queso fresco and diced avocado after baking. Serve with warm corn tortillas for scooping up the spicy, creamy mixture. 🌵
Nutrition facts
Frequently asked questions
Why does America's Test Kitchen make the sauce from scratch instead of using canned soup?
Canned soup often contains excess salt and preservatives that can make the sauce taste flat or overly salty. The homemade version uses fresh mushrooms, cream, and mustard for a richer, more balanced flavor with proper thickness—no watery surprises during baking!
Can I use frozen green beans instead of fresh?
Yes, but with adjustments! Use 2 cups frozen green beans (thawed and drained) instead of fresh. Skip the blanching step and pat them very dry to prevent a soggy casserole. The texture will be slightly different but still delicious.
How do I keep the fried onions extra crispy?
Fry them in small batches over medium heat until deep golden brown (not just light brown). Drain on paper towels, then spread them out on a wire rack to cool completely before assembling. This prevents steam from making them soggy during baking.
Can I make this ahead for Thanksgiving?
Assemble the casserole (unbaked) up to 24 hours ahead and refrigerate. Add 15-20 minutes to baking time (cover loosely with foil) to account for the cold start. The flavors will deepen overnight, and the texture remains perfect.
What if my casserole turns out too watery?
If the sauce seems thin after baking, sprinkle 1 tbsp cornstarch mixed with 1 tbsp cold water over the top and bake 5-10 minutes more. For future batches, ensure your mushrooms are fully cooked and the sauce thickens properly before assembling.