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Southern-Style Green Bean Casserole

Tender-crisp beans and a deeply savory mushroom sauce meet a crisp, freshly fried onion topping in this potluck casserole.

Fresh green beans and browned mushrooms sit in cream sauce beneath a crisp golden onion topping.

This from-scratch casserole keeps the familiar creamy, savory center while using fresh beans and a homemade onion topping. Blanching first gives the beans a head start without asking them to soften in the sauce.

Blanch, chill, and dry

A brief boil seasons the green beans and starts their cooking, while the ice bath stops them before they lose their bite. Drying matters just as much: wet beans thin the sauce and make the casserole watery at the edges.

Fry a crisp onion finish

Buttermilk softens the sliced onion's sharpness and helps a light flour coating cling. Fry in small batches so the oil stays hot enough to crisp the rings instead of steaming them.

Blanched green beans are folded through a thick mushroom cream sauce before baking. — Fresh beans are folded through the creamy mushroom sauce before baking.

Build savory depth

Give the mushrooms time to release and cook off their liquid before thickening the sauce. Their browned edges add depth, while the flour, milk, and broth create a coating that clings to the beans.

Make the components ahead

The beans and sauce can be prepared a day ahead and kept in separate covered containers in the refrigerator. Warm the sauce gently before folding in the beans; keeping the components separate prevents the beans from continuing to soften in the sauce.

Golden crisp onion rings rest over bubbling mushroom sauce with bright green beans. — Crisp golden onion rings crown the bubbling mushroom sauce and green beans.

Southern-Style Green Bean Casserole

8 servings

100 minutes total

Ingredients

• 2 lb fresh green beans, trimmed and cut into short lengths
• 1 tbsp kosher salt, for blanching water
• 4 tbsp unsalted butter
• 12 oz cremini mushrooms, finely chopped
• 1 small yellow onion, finely diced
• 2 garlic cloves, minced
• 3/4 cup all-purpose flour
• 2 cups whole milk
• 1 cup low-sodium vegetable broth
• 1 tbsp soy sauce
• 1 tsp kosher salt
• 1/2 tsp black pepper
• 1/4 tsp ground nutmeg
• 1 large yellow onion, thinly sliced
• 1/2 cup buttermilk
• 2 cups neutral oil, for frying

Method

Heat the oven
Set a rack in the center and heat the oven to 375 F. Butter is not needed for the casserole dish; the sauce will coat it fully.
Look for: The oven is fully preheated and the casserole dish is ready nearby.
Blanch the beans
Bring a large pot of water to a boil, add the kosher salt and green beans, and cook for 4 minutes. Transfer the beans to ice water, then drain and dry them well so the sauce stays creamy.
Look for: The beans are bright green and bend slightly but still resist a bite.
Soak the onion
Separate the thin onion slices into rings and cover them with the buttermilk. Let them soak while you prepare the casserole base, which softens their sharpness and helps the coating adhere.
Look for: The onion rings are submerged and the buttermilk clings to their surfaces.
Fry the onion topping
Heat the neutral oil in a heavy saucepan to 350 F. Drain the onion rings, toss them with 1/2 cup of the flour, and fry in small batches for 2 to 3 minutes until crisp and golden; drain on a rack.
Look for: The coating is crisp and pale gold, and the rings are not crowded in the oil.
Brown the mushrooms
Melt the butter in a wide skillet over medium-high heat. Add the mushrooms and cook until their released liquid evaporates and browned edges appear, then stir in the diced yellow onion and cook until soft; add the garlic for the final 30 seconds.
Look for: The skillet is mostly dry, the mushrooms are browned, and the garlic smells fragrant rather than raw.
Make the mushroom sauce
Sprinkle the remaining 1/4 cup flour over the mushroom mixture and stir for 1 minute. Gradually whisk in the milk and broth; simmer until thick enough to coat a spoon, then season with soy sauce, kosher salt, pepper, and nutmeg.
Look for: The sauce is smooth and spoon-coating, with no dry flour pockets or raw flour aroma.
Assemble and bake
Fold the dry green beans into the mushroom sauce until coated, then spread the mixture in a casserole dish. Bake uncovered at 375 F for 20 minutes, until the edges bubble and the center is hot.
Look for: Bubbles break around the edges and the beans remain vivid beneath the sauce.
Crisp the topping
Scatter the fried onion rings evenly over the casserole and return it to the 375 F oven for 5 minutes. The topping should warm and stay crisp while the sauce bubbles beneath it.
Look for: The onion topping is fragrant and crisp, with bubbling sauce visible at the edges.
Rest and serve
Rest the casserole for 10 minutes so the sauce settles enough to scoop cleanly. Serve warm, lifting from the bottom to bring beans, mushroom sauce, and crisp onions into each portion.
Look for: The sauce holds softly around the beans and the onion topping remains crunchy.