Green Bean Casserole From Scratch With Crispy Onions

What makes this green bean casserole from scratch work?

Green Bean Casserole From Scratch serves 10 and takes 1 hour 10 minutes. Blanching the beans first locks in color and prevents them from overcooking while the casserole browns. A roux-thickened mushroom sauce stays creamy enough to coat each bean without pooling in the dish. ^[1]

Ingredients

For 10 servings: 2 pounds green beans, trimmed and halved; 1 tablespoon kosher salt for the water plus 3/4 teaspoon for seasoning; 3 tablespoons unsalted butter; 12 ounces cremini mushrooms, sliced; 1 small shallot, minced; 2 garlic cloves, minced; 3 tablespoons all-purpose flour; 2 cups whole milk; 1 cup low-sodium vegetable broth; 1 teaspoon soy sauce; 1/2 teaspoon black pepper; 1 1/2 cups crispy fried onions. Measure and prepare every ingredient before cooking so the method moves cleanly and the final seasoning remains controlled. ^[1]

Step-by-step method

1. Heat the oven to 375°F. Boil a large pot of salted water and prepare ice water. Blanch beans 4 minutes, drain and chill; dry well. ^[1]

2. Melt butter in a wide skillet. Brown mushrooms for 8 to 10 minutes, then add shallot and garlic for 2 minutes. ^[1]

3. Sprinkle flour over the mushrooms and cook 1 minute. Gradually whisk in milk and broth. Simmer until the sauce coats a spoon, then season with soy sauce, pepper and salt. ^[1]

4. Fold beans and 1/2 cup fried onions into the sauce. Transfer to a 9-by-13-inch dish and bake 25 minutes. ^[1]

5. Top with the remaining onions and bake 8 to 10 minutes, watching closely, until bubbling and crisp. ^[1]

Make ahead, substitutions and storage

Blanch the beans and make the mushroom sauce up to two days ahead; refrigerate separately. Assemble without the onion topping up to one day ahead. Use gluten-free flour and certified gluten-free onions if needed. Refrigerate leftovers within two hours, keep three to four days and reheat to 165°F. ^{[1] [2]}

Transfer green bean casserole leftovers to shallow containers within two hours and refrigerate for no more than four days. Reheat to 165°F, adding fresh fried onions only near the end so the topping stays crisp. If assembling ahead, keep the sauce, beans and topping separate until baking day. ^[2]