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The mushrooms hiss in the pan, then suddenly go quiet as their liquid cooks away. That’s the moment I watch for in this Bon Appetit Green Bean Casserole: mushrooms with their moisture cooked off make a deeper, more savory sauce instead of a watery one. The fresh beans keep their bite, and the crisp shallots bring the crunch that makes every spoonful feel finished.

I like that the parts each get their own attention before they meet in the baking dish. The beans get a quick blanch, the mushrooms cook down, and the sauce thickens on the stove before it goes into the oven. That way, the casserole comes out bubbling at the edges with green beans that still have some snap and a sauce that clings instead of pooling.

Why the Green Beans Should Still Have Some Snap Before They Go in the Oven

It’s easy to assume the beans should be fully tender before they meet the sauce. Here, that would leave them with little structure after another stretch in the oven. A brief blanch softens the raw edge and turns the beans bright green, but keeps a little firmness in the center. The bake then finishes them without pushing them toward mushy.

That crisp-tender starting point also gives the sauce a job: it coats the beans as they bake rather than having to rescue overcooked vegetables. Fresh beans are especially helpful because you can control how far they cook before assembly. Drain them well after blanching, too; water clinging to the beans can loosen the sauce in the dish.

The finished casserole should be bubbling at the edges, with beans that still hold their shape when you lift them out. If you prefer softer green beans, blanch them toward the longer end of the range, but don’t cook them until completely tender in the pot.

What the Mushrooms, Milk, and Shallots Each Bring to the Casserole

• Fresh green beans — Their firm texture stands up to blanching and baking better than already-soft canned beans. Trim and cut them evenly so the pieces cook at about the same rate.
• Cremini mushrooms — These bring an earthy, savory base to the sauce. Finely chop them so they distribute through the casserole instead of leaving large, slippery pieces; cremini are worth choosing for their fuller flavor, though white mushrooms will work in a pinch.
• Shallots and cornstarch — Shallots fry into a delicate, sweet-edged topping, while cornstarch gives their thin rings a crisp coating. Separate the rings before tossing so they’re coated all around.
• Chicken broth, whole milk, and flour — Broth adds savory depth, whole milk makes the sauce creamy, and flour thickens the liquid into a coating sauce. Whole milk gives a fuller result than lower-fat milk, while all-purpose flour is the dependable choice for this roux-style sauce.
• Soy sauce — A small amount adds savory depth to the mushroom sauce without making it taste overtly like soy. Use regular soy sauce rather than a sweetened variety.

Building the Mushroom Sauce Before the Casserole Goes in the Oven

Fry the Shallots Until Golden

Separate the shallot rings and toss them with the cornstarch, shaking off the excess. Heat the neutral oil in a 2-quart saucepan over medium heat to 325°F. Fry the rings in batches for 2 to 3 minutes per batch, keeping the oil near that temperature. Lift them out when they’re golden and transfer them to a paper towel-lined plate; they’ll continue to darken a little as they cool.

Blanch the Beans Just Until Crisp-Tender

Bring the water and 1 tablespoon of kosher salt to a boil in an 8-quart stockpot. Add the cut green beans and cook for 3 to 4 minutes, looking for vivid green color and a tender outside with a slight bite inside. Drain them well rather than letting them sit in the hot water. Have the oven heating to 375°F while you prepare the sauce.

Cook Down the Mushrooms and Thicken the Sauce

Grease a 9×13-inch baking dish with 1 tablespoon of butter. Melt the remaining butter in a 4-quart saucepan over medium-high heat, add the finely chopped mushrooms, and cook for 8 to 10 minutes, stirring occasionally, until their liquid has evaporated. Add the garlic for 30 seconds, then stir in the flour and cook it for 1 minute. Gradually whisk in the broth and milk, then add the soy sauce, remaining salt, and pepper; simmer for 5 to 7 minutes, whisking often, until the sauce coats the back of a spoon.

Bake Until the Edges Bubble

Add the green beans to the prepared dish, pour the sauce over them, and stir gently until they’re coated. Bake uncovered for 25 to 30 minutes, until you see bubbles around the edges. Scatter the crispy shallots over the top once the casserole comes out of the oven. Let it rest for 10 minutes before serving so the sauce settles around the beans.

Simple Swaps for a Vegetarian or Gluten-Free Green Bean Casserole

Questions That Come Up When Making Green Bean Casserole

Bon Appetit Green Bean Casserole

Green bean casserole with crispy shallots pairs bright, crisp-tender green beans with a creamy mushroom sauce. The casserole bakes uncovered until bubbling around the edges, then gets topped with golden fried shallots.

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Prep Time 20 minutes mins

Cook Time 56 minutes mins

Resting time 10 minutes mins

Total Time 1 hour hr 26 minutes mins

Servings: 8 servings

Course: Side Dish

Cuisine: American

Calories: 300

Ingredients Equipment Method Notes

Ingredients

  

For the crispy shallots

• 3 shallots large, about 8 ounces, peeled and sliced into 1/8-inch-thick rings
• 0.33 cup cornstarch
• 2 cups neutral oil such as canola

For the casserole

• 4 qt water
• 1 tbsp kosher salt divided
• 0.5 tsp kosher salt divided
• 2 lb fresh green beans trimmed and cut into 2-inch pieces
• 4 tbsp unsalted butter divided
• 1 lb cremini mushrooms finely chopped
• 3 cloves garlic minced
• 0.25 cup all-purpose flour
• 1.5 cups low-sodium chicken broth
• 1.5 cups whole milk
• 1 tbsp soy sauce
• 0.5 tsp freshly ground black pepper

Equipment

• 1 2-quart saucepan
• 1 8-quart stockpot
• 1 9x13-inch baking dish
• 1 4-quart saucepan

Method

 

Fry the shallots

1. Separate the shallot rings and toss them with the cornstarch until lightly coated, shaking off excess.
2. Heat the oil in a 2-quart saucepan over medium heat to 325°F.
3. Fry the shallots in batches, maintaining the oil temperature, for 2 to 3 minutes per batch until golden, then transfer to a paper towel-lined plate.

Blanch the green beans

1. Heat the oven to 375°F.
2. Bring the water and 1 tablespoon of the salt to a boil in an 8-quart stockpot.
3. Add the green beans and cook for 3 to 4 minutes until bright green and crisp-tender, then drain well.

Make the mushroom sauce

1. Grease a 9x13-inch baking dish with 1 tablespoon of the butter.
2. Melt the remaining 3 tablespoons butter in a 4-quart saucepan over medium-high heat.
3. Add the mushrooms and cook for 8 to 10 minutes, stirring occasionally, until their liquid evaporates.
4. Add the garlic and cook for 30 seconds.
5. Stir in the flour and cook for 1 minute.
6. Gradually whisk in the broth and milk, then stir in the soy sauce, remaining 1/2 teaspoon salt, and pepper.
7. Simmer, whisking often, for 5 to 7 minutes until the sauce thickens enough to coat the back of a spoon.

Assemble and bake

1. Add the green beans to the prepared baking dish, pour the sauce over them, and stir gently to coat.
2. Bake uncovered for 25 to 30 minutes until bubbling around the edges.
3. Scatter the crispy shallots over the casserole and let it rest for 10 minutes before serving.

Notes

For the crispest topping, maintain the oil temperature while frying the shallots in batches. Refrigerate leftovers for up to 3 days; freezing is not recommended because the sauce and green beans can lose their texture. For a vegetarian version, use vegetable broth in place of chicken broth.