Martha Stewart String Bean Casserole Recipe

By anabelle

Fact checked by Edward Harrington

Updated October 29, 2026

This Martha Stewart string bean casserole is a from-scratch take on the holiday classic, made with tender-crisp green beans, a silky mushroom cream sauce, and a pile of crispy fried onions on top. The sauce is savory and rich with Parmesan and a hint of nutmeg, and the beans keep a little snap instead of turning to mush. It’s inspired by Martha Stewart’s straightforward American home cooking, and it’s the kind of side dish that earns a spot next to the turkey.

You’ll need 70 minutes from start to finish, including 20 minutes of prep, and most of that time is hands-off oven work. The steps are simple enough for a weeknight but special enough for Thanksgiving, Christmas, or a potluck where you want to bring something people remember.

Why This Martha Stewart String Bean Casserole Works

The big difference here is the sauce. Instead of opening a can, you build a mushroom cream sauce from a simple butter-and-flour roux, then whisk in chicken broth, whole milk, and Parmesan until it’s thick enough to coat a spoon.

Blanching the string beans first and shocking them in ice water is the other key move. It sets their color and texture so they finish cooking in the oven without going soft, and the crispy onion topping goes on at the very end so it stays crunchy.

What You’ll Love About It

Three things stand out: a made-from-scratch mushroom sauce that tastes far fresher than the canned version, green beans that stay bright and tender-crisp, and a buttery fried-onion topping that’s worth the extra pan. It also assembles a day ahead, which makes holiday cooking calmer.

Ingredients

You’ll need 20 ingredients, split between the crispy topping and the casserole itself.

For the Crispy Onion Topping

• 2 tablespoons (28g) unsalted butter — for softening the onion.
• 1 medium yellow onion, thinly sliced (about 1 1/2 cups)
• 1/2 cup (63g) all-purpose flour
• 1/2 teaspoon kosher salt
• 1/4 teaspoon freshly ground black pepper
• 1/4 teaspoon smoked paprika — adds a gentle smoky note.
• 1 cup (240ml) whole milk — for dipping the onion slices.
• 1 cup (120g) panko breadcrumbs — for the baked topping option.

For the Casserole

• 1 1/2 pounds (680g) fresh string beans, trimmed and cut into 2-inch pieces
• 2 tablespoons (28g) unsalted butter
• 8 ounces (227g) cremini mushrooms, thinly sliced
• 1 small yellow onion, finely chopped (about 1/2 cup)
• 2 cloves garlic, minced
• 1/4 cup (31g) all-purpose flour
• 1 1/2 cups (360ml) chicken broth
• 1 cup (240ml) whole milk
• 1/2 teaspoon kosher salt
• 1/4 teaspoon freshly ground black pepper
• 1/4 teaspoon freshly grated nutmeg — a small amount goes a long way in a cream sauce.
• 1/2 cup (57g) grated Parmesan cheese

Equipment

• Large skillet — for softening the topping onion.
• Deep skillet — for frying, with 1 inch of oil.
• Large saucepan — for the mushroom sauce.
• Large pot — for blanching the string beans.
• 9×13-inch (23x33cm) baking dish — buttered before filling.
• Sheet pan — if you choose the baked topping.
• Wire rack or paper towels — for draining the fried onions.

How to Make Martha Stewart String Bean Casserole

Step 1: Soften the Topping Onion

Melt 2 tablespoons butter in a large skillet over medium heat. Add the thinly sliced onion and cook, stirring occasionally, until soft and golden, 8 to 10 minutes. Keep the heat moderate; if the onion browns too fast it turns bitter. While it cooks, stir together the flour, 1/2 teaspoon salt, pepper, and smoked paprika in a shallow dish.

Step 2: Coat and Crisp the Onions

Dip the softened onion slices in the milk, then dredge in the flour mixture, shaking off the excess. Heat 1 inch of vegetable oil in a deep skillet to 350°F (175°C) and fry the coated onions in batches until golden and crisp, about 2 minutes per batch. Drain on paper towels and season with a pinch of salt. Alternatively, toss the coated onions with the panko and bake on a sheet pan at 400°F (205°C) until crisp, about 12 minutes.

Step 3: Blanch the String Beans

Preheat the oven to 350°F (175°C) and butter a 9×13-inch (23x33cm) baking dish. Bring a large pot of salted water to a boil, add the string beans, and cook until just tender-crisp, 4 to 5 minutes. Drain and immediately plunge them into ice water to stop the cooking, then drain well and pat dry.

Step 4: Start the Mushroom Sauce

In a large saucepan, melt 2 tablespoons butter over medium heat. Add the mushrooms and cook, stirring, until they release their liquid and begin to brown, 6 to 8 minutes. Add the chopped onion and garlic and cook until softened, about 3 minutes more.

Step 5: Thicken the Sauce

Sprinkle the flour over the mushroom mixture and cook, stirring constantly, for 1 minute to cook out the raw flour taste. Gradually whisk in the chicken broth, then the milk, and bring to a simmer. Cook, whisking often, until the sauce thickens enough to coat the back of a spoon, 4 to 5 minutes.

Step 6: Season and Add the Beans

Stir in the 1/2 teaspoon salt, pepper, nutmeg, and Parmesan until the cheese melts. Taste and adjust the seasoning; the sauce should be creamy and well seasoned. Fold in the blanched string beans until evenly coated.

Step 7: Bake Until Bubbling

Transfer the mixture to the prepared baking dish and spread it in an even layer. Bake until bubbling at the edges and heated through, 20 to 25 minutes. If the casserole looks dry, stir in a splash of broth before baking.

Step 8: Add the Topping and Rest

Scatter the crispy onion topping over the casserole and bake 5 minutes more, just until the topping is warm and fragrant; don’t let it burn. Let it rest 5 minutes before serving.

What to Serve With It

This belongs next to roast turkey, roast chicken, or a glazed centerpiece, and it pairs well with mashed potatoes, stuffing, and cranberry sauce. For a weeknight, serve it with a simple roast chicken and warm dinner rolls. A pitcher of lemonade or iced tea works well at a potluck.

Tips for the Best Results

• Dry the beans — pat them thoroughly so the sauce doesn’t turn watery.
• Watch the oil — keep it at 350°F (175°C) so the onions crisp without burning.
• Whisk constantly — add the broth and milk gradually to avoid lumps.
• Season to taste — adjust salt after the Parmesan goes in.
• Top at the end — add the onions in the final 5 minutes only.
• Rest before serving — five minutes lets the sauce settle and thicken.

Easy Variations

• Baked topping — skip frying and bake the panko-coated onions for 12 minutes.
• Extra mushrooms — add up to 4 ounces (113g) more cremini for a meatier sauce.
• Sharper cheese — swap in 1/2 cup (50g) grated Gruyère for a richer flavor.
• Frozen beans — use 1 1/2 pounds (680g) frozen string beans and skip the blanching.

Storing and Reheating

• Refrigerator — keep leftovers in an airtight container for up to 3 days.
• Freezer — freeze the unbaked casserole, without topping, for up to 2 months.
• Make ahead — assemble up to 1 day ahead and refrigerate; add topping before baking.
• Reheating — cover with foil and warm at 350°F (175°C) for 20 to 25 minutes to 165°F (74°C).

Nutrition (per serving)

These values are estimates per serving and will vary with your exact ingredients.

FAQs

Where did string bean casserole come from?

The dish became a holiday staple in the United States in the mid-20th century, when home cooks started combining canned green beans and condensed soup with a crispy onion topping. The from-scratch version here keeps those familiar flavors but builds the sauce fresh.

Can I make this Martha Stewart string bean casserole recipe ahead of time?

Yes, assemble the casserole up to 1 day ahead, cover, and refrigerate. Keep the crispy topping separate and add it just before the final bake so it stays crisp.

Can I use frozen or canned string beans?

Frozen string beans work well; use the same 1 1/2 pounds (680g) and skip the blanching step. Canned beans turn soft quickly, so drain them well and reduce the bake time slightly.

Why is my casserole dry or watery?

A watery casserole usually means the beans weren’t dried well after blanching, or the sauce was too thin. Dry the beans thoroughly and simmer the sauce until it coats a spoon before folding everything together.

Martha Stewart-Inspired String Bean Casserole

Print Recipe

A from-scratch green bean casserole with a silky mushroom cream sauce, tender-crisp string beans, and a buttery, crispy fried-onion topping. Inspired by Martha Stewart’s classic American home cooking, this version skips the canned soup for a fresher, more elegant take on the holiday favorite.

• Author: Anabelle McLean
• Prep Time: 20
• Cook Time: 50
• Total Time: 70
• Yield: 8 1x
• Category: Side Dish
• Method: Baking
• Cuisine: American

Ingredients

Scale 1x2x3x

For the Topping

• 2 tablespoons (28g) unsalted butter
• 1 medium yellow onion, thinly sliced (about 1 1/2 cups)
• 1/2 cup (63g) all-purpose flour
• 1/2 teaspoon kosher salt
• 1/4 teaspoon freshly ground black pepper
• 1/4 teaspoon smoked paprika
• 1 cup (240ml) whole milk
• 1 cup (120g) panko breadcrumbs

For the Casserole

• 1 1/2 pounds (680g) fresh string beans, trimmed and cut into 2-inch pieces
• 2 tablespoons (28g) unsalted butter
• 8 ounces (227g) cremini mushrooms, thinly sliced
• 1 small yellow onion, finely chopped (about 1/2 cup)
• 2 cloves garlic, minced
• 1/4 cup (31g) all-purpose flour
• 1 1/2 cups (360ml) chicken broth
• 1 cup (240ml) whole milk
• 1/2 teaspoon kosher salt
• 1/4 teaspoon freshly ground black pepper
• 1/4 teaspoon freshly grated nutmeg
• 1/2 cup (57g) grated Parmesan cheese

Instructions

1. Make the crispy topping: Melt 2 tablespoons butter in a large skillet over medium heat. Add the thinly sliced onion and cook, stirring occasionally, until soft and golden, 8 to 10 minutes; do not let it brown too fast or it will turn bitter. Meanwhile, in a shallow dish, stir together the flour, 1/2 teaspoon salt, pepper, and smoked paprika.
2. Dip the softened onion slices in the milk, then dredge in the flour mixture, shaking off excess. Heat 1 inch of vegetable oil in a deep skillet to 350°F (175°C) and fry the coated onions in batches until golden and crisp, about 2 minutes per batch. Drain on paper towels; season with a pinch of salt. (Alternatively, toss the coated onions with the panko and bake on a sheet pan at 400°F (205°C) until crisp, about 12 minutes.)
3. Preheat the oven to 350°F (175°C) and butter a 9×13-inch (23x33cm) baking dish. Bring a large pot of salted water to a boil, add the string beans, and cook until just tender-crisp, 4 to 5 minutes. Drain and immediately plunge into ice water to stop the cooking, then drain well and pat dry.
4. Make the sauce: In a large saucepan, melt 2 tablespoons butter over medium heat. Add the mushrooms and cook, stirring, until they release their liquid and begin to brown, 6 to 8 minutes. Add the chopped onion and garlic and cook until softened, about 3 minutes more.
5. Sprinkle the flour over the mushroom mixture and cook, stirring constantly, for 1 minute to cook out the raw flour taste. Gradually whisk in the chicken broth, then the milk, and bring to a simmer. Cook, whisking often, until the sauce thickens enough to coat the back of a spoon, 4 to 5 minutes.
6. Stir in the 1/2 teaspoon salt, pepper, nutmeg, and Parmesan until the cheese melts. Taste and adjust seasoning; the sauce should be creamy and well seasoned. Fold in the blanched string beans until evenly coated.
7. Transfer the mixture to the prepared baking dish and spread in an even layer. Bake until bubbling at the edges and heated through, 20 to 25 minutes. If the casserole looks dry, stir in a splash of broth before baking.
8. Scatter the crispy onion topping over the casserole and bake 5 minutes more, just until the topping is warm and fragrant; do not let it burn. Let rest 5 minutes before serving.

Notes

Storage: Refrigerate leftovers in an airtight container for up to 3 days. Freeze the unbaked casserole (without topping) for up to 2 months; thaw overnight in the refrigerator before baking. Make-ahead: The casserole can be assembled up to 1 day ahead and refrigerated; add the topping just before baking. Reheat covered with foil at 350°F (175°C) for 20 to 25 minutes, then uncover for the last 5 minutes to crisp the topping.

Nutrition

• Calories: 305
• Sugar: 7g
• Sodium: 480mg
• Saturated Fat: 7g
• Carbohydrates: 36g
• Fiber: 4g
• Protein: 10g
• Cholesterol: 28mg

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