Green bean casserole is a beloved classic side dish especially popular during holiday gatherings. Its creamy mushroom sauce, tender green beans, and crispy fried onion topping create a perfect balance of textures and flavors that satisfy large crowds with ease. This recipe is scaled to serve 20 people, ideal for big family dinners or potlucks.
Ingredients
- 8 pounds fresh green beans, trimmed and cut into 2-inch pieces (or 6 pounds frozen green beans, thawed)
- 6 tablespoons unsalted butter
- 6 cups sliced white mushrooms (about 1 1/2 pounds)
- 2 large onions, finely chopped
- 1/2 cup all-purpose flour
- 6 cups low-sodium chicken broth or vegetable broth
- 3 cups whole milk
- 3 teaspoons kosher salt, divided
- 1 1/2 teaspoons ground black pepper, divided
- 8 cups French fried onions (divided, about 2 standard 6-ounce cans)
- Optional: 1 teaspoon garlic powder or 1 teaspoon onion powder for extra flavor
Instructions
- Preheat the oven: Set your oven to 350°F (175°C) and lightly grease two 9×13-inch casserole dishes or one very large roasting pan.
- Prepare the green beans: If using fresh green beans, blanch them in boiling salted water for 4-5 minutes until just tender but still crisp. Drain and immediately plunge into ice water to stop cooking. If using frozen, thaw and drain well.
- Cook mushrooms and onions: In a large skillet or sauté pan, melt the butter over medium heat. Add the chopped onions and cook until translucent, about 4-5 minutes. Add the sliced mushrooms and cook until they release their moisture and become golden brown, about 8-10 minutes.
- Make the sauce: Sprinkle the flour over the mushroom and onion mixture and stir constantly for 2 minutes to cook out the raw flour taste. Gradually whisk in the chicken broth and milk, continuing to whisk until the sauce thickens and bubbles, about 5-7 minutes. Season with 2 teaspoons salt and 1/2 teaspoon pepper (plus garlic or onion powder if using). Remove from heat.
- Combine green beans and sauce: In a large mixing bowl or directly in the casserole dishes, combine the blanched green beans with the mushroom sauce. Stir gently to coat all the beans evenly.
- Assemble the casserole: Pour the green bean mixture into the prepared casserole dishes. Spread it evenly. Sprinkle 4 cups of French fried onions over the top.
- Bake: Place the casseroles on the middle oven racks and bake uncovered for 25 minutes until the sauce is bubbly and the onions on top begin to brown.
- Add remaining onions and finish baking: Remove casseroles from the oven, sprinkle the remaining 4 cups of French fried onions on top for extra crunch, and bake for another 5-7 minutes until golden brown.
- Serve warm: Let the casseroles rest for 5 minutes before serving. This allows the sauce to set slightly and makes serving easier.
Tips
- Substitutions: Use frozen green beans if fresh are not available. They save prep time and work well when thawed and drained thoroughly. For a dairy-free version, substitute butter with olive oil and use a plant-based milk.
- Make ahead: You can prepare the mushroom sauce and green beans a day in advance. Assemble the casserole, cover tightly, and refrigerate. Add the fried onions and bake just before serving.
- Common mistake: Avoid overcooking the green beans during blanching; they should be crisp-tender to prevent the casserole from becoming mushy after baking.
- Even baking: Use two smaller casserole dishes instead of one large one for more even cooking, especially if your oven has hot spots.
Serving Suggestions
This green bean casserole pairs beautifully with traditional holiday mains like roasted turkey, baked ham, or roast chicken. For a complete meal, serve alongside mashed potatoes or sweet potato casserole. A fresh cranberry sauce or a simple mixed green salad can add a bright contrast to the creamy casserole. For potlucks, provide serving spoons and small plates so guests can help themselves easily.
Variations
To customize this classic dish, try adding cooked and crumbled bacon for smoky flavor or a handful of toasted sliced almonds for extra crunch. Swap out the French fried onions for homemade crispy shallots or panko breadcrumbs mixed with melted butter for a lighter topping. For a more gourmet twist, stir in some shredded Gruyère or sharp cheddar cheese into the sauce before baking. Vegetarian or vegan versions can use vegetable broth and plant-based milk and butter substitutes.
Storage and Reheating
Store leftover green bean casserole in an airtight container in the refrigerator for up to 3 days. To reheat, cover loosely with foil and warm in a 350°F (175°C) oven for 15-20 minutes until heated through. Avoid microwaving large portions as this can cause uneven heating and soggy topping. If frozen, wrap tightly and freeze for up to 2 months; thaw overnight in the refrigerator before reheating as above.
Frequently Asked Questions
Can I use canned green beans instead of fresh or frozen?
While canned green beans can be used in a pinch, they tend to be softer and more watery, which may result in a mushier casserole. If using canned, drain them very well and reduce the liquid in the sauce slightly to compensate.
Is it better to make this casserole ahead of time?
Yes, assembling the casserole a day before can save time on the day of your event. Keep it covered and refrigerated, then add the crispy onions just before baking to maintain their crunch.
How do I keep the fried onions crispy?
Adding the fried onions in two stages—half before baking and the rest near the end—helps keep the topping crisp. Avoid covering the casserole tightly while hot, as trapped steam can soften the onions.
Can this recipe be doubled or halved easily?
This recipe is already scaled for 20 servings, but it can be halved or doubled. Just adjust the size and number of casserole dishes accordingly and monitor baking times, as larger casseroles may require slightly longer baking.
What if I don’t have fresh mushrooms?
Dried mushrooms rehydrated in warm water can add a concentrated flavor, but fresh mushrooms provide the best texture and moisture. If unavailable, you can omit mushrooms altogether, though the casserole will be less rich.
Can I make this gluten-free?
Yes, substitute the all-purpose flour with a gluten-free flour blend or cornstarch (use about half the amount for cornstarch) to thicken the sauce. Ensure the fried onions are gluten-free or make your own using gluten-free breading.
With these detailed instructions and tips, preparing green bean casserole for a crowd becomes manageable and rewarding. This comforting dish continues to be a holiday favorite because it combines simple ingredients into a rich, flavorful side that complements any festive meal perfectly.
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