Green Bean Casserole

A low FODMAP green bean casserole with a scratch cream sauce of gluten-free flour, broth, cream, and lactose-free milk under a crispy leek-green and panko topping.

Prep 20 min

Cook 40 min

Serves 8

Gluten-free

Ingredients

Casserole

• 1 1/3 lb (600 g) fresh green beans, trimmed and cut into 2-inch pieces
• 1 tablespoon kosher salt, for the blanching water
• 2 tablespoons unsalted butter
• 2 tablespoons garlic-infused olive oil
• 3 tablespoons gluten-free all-purpose flour (or 2 tablespoons cornstarch)
• 1 cup (240 ml) low-FODMAP chicken broth
• 1 cup (240 ml) heavy cream
• 1 cup (240 ml) lactose-free whole milk
• 1 teaspoon fine salt, plus more to taste
• 1/2 teaspoon freshly ground black pepper
• 1/4 teaspoon freshly grated nutmeg
• 2 teaspoons gluten-free tamari or certified gluten-free soy sauce

Crispy Leek-Green Topping

• 2 large leeks, green tops only, cut into thin matchsticks (about 2 cups)
• 2 tablespoons garlic-infused olive oil
• 1/2 cup (40 g) gluten-free panko or plain gluten-free breadcrumbs
• 1/4 cup (25 g) finely grated Parmesan
• 1/4 teaspoon fine salt
• 1 teaspoon butter, for the dish

Instructions

Blanch the Green Beans

1. Bring a large pot of water to a rolling boil and add the kosher salt. Set a large bowl of ice water next to the stove.
2. Drop the green beans into the boiling water and cook for 4 to 5 minutes, until bright green and just tender.
3. Drain and transfer immediately to the ice bath. Once cool, drain again and pat dry with a clean towel. Set aside.

Make the Cream Sauce

1. Melt the butter with the garlic-infused olive oil in a medium saucepan over medium heat.
2. Whisk in the gluten-free flour and cook, whisking constantly, for 90 seconds. The roux should smell toasty and turn a shade darker.
3. Pour in the chicken broth in a slow stream, whisking until smooth. Add the heavy cream and lactose-free milk the same way.
4. Bring to a gentle simmer and cook for 4 to 5 minutes, whisking often, until the sauce coats the back of a spoon.
5. Stir in the salt, pepper, nutmeg, and soy sauce. Taste and adjust. Pull off the heat.

Crisp the Leek Greens

1. Heat the garlic-infused olive oil in a wide skillet over medium heat.
2. Add the leek-green matchsticks and cook, stirring often, for 6 to 8 minutes, until deeply golden and crisp at the edges. Watch them in the last two minutes; they go from golden to burnt fast.
3. Transfer to a paper-towel-lined plate and season with a pinch of salt.
4. In a small bowl, toss the breadcrumbs, Parmesan, and 1/4 teaspoon salt together. Keep the crispy leek greens aside for the end so they don't burn in the oven.

Assemble and Bake

1. Heat the oven to 375°F (190°C). Grease a 3-quart (9x13-inch) baking dish with the teaspoon of butter.
2. Combine the blanched green beans and cream sauce in the baking dish and stir to coat every piece.
3. Scatter the breadcrumb-Parmesan mixture evenly over the top.
4. Bake for 20 minutes, until the sauce is bubbling at the edges and the topping is golden.
5. Scatter the crispy leek greens over the hot casserole and serve.

Tips & Substitutions

• Do not use canned cream-of-mushroom soup. Most brands contain button mushrooms, onion, and garlic, which are all high FODMAP. The scratch sauce here takes 10 minutes and gives you a creamy base without them.
• No French's fried onions. Fried onion strings are mostly onion, which is high in fructans, in a wheat-flour coating that isn't gluten-free. Crispy leek greens and gluten-free breadcrumbs give you the crunch and the onion flavor instead.
• Leek greens only, not whites. The dark green tops are low FODMAP at 1 cup (75 g) per serve, while the white bulb is high FODMAP like an onion. Trim where the stalk turns dark green and discard the whites or save them for someone not on the diet.
• Cornstarch swap for a silkier sauce. Replace the 3 tablespoons of gluten-free flour with 2 tablespoons of cornstarch slurried into 2 to 3 tablespoons of cold broth or cold milk. Skip the roux; whisk the slurry into the hot dairy-and-broth mixture and simmer 1 to 2 minutes until thickened.
• Fresh beans over frozen or canned. Fresh green beans hold their snap through blanching and baking. Frozen work if thawed and patted very dry; canned beans turn to mush in the oven.
• Make ahead. Blanch the beans and make the sauce a day ahead, refrigerated separately, and crisp the leeks the day of. Bake straight from the fridge, adding 5 to 7 minutes.

Why This Works

Green beans are low-FODMAP at a normal serve. Monash rates common (string) green beans as low at 15 beans or 75 g per serve. This recipe uses 600 g across 8 servings, so each portion is right at that 75 g mark.

A small amount of cream. An eighth of this casserole has about 2 tablespoons of cream, a low FODMAP amount, and the rest of the dairy is lactose-free milk.

Lactose-free milk and a scratch roux replace the can. Canned cream-of-mushroom soup contains button mushrooms, onion, and garlic, all high FODMAP. Lactose-free milk, a gluten-free roux, and garlic-infused oil rebuild the body and flavor without them.

Infused oil carries the garlic flavor. Garlic's fructans dissolve in water but not in oil, so strained garlic-infused oil stands in for minced garlic.

Storage

Refrigerate leftovers in a sealed container for up to 3 days at 40°F (4°C) or below. Reheat individual portions in the microwave or cover and warm in a 350°F (175°C) oven for 12 to 15 minutes. The topping softens overnight; a 2-minute pass under the broiler after reheating brings the crunch back. It doesn't freeze well, since the beans go limp and the sauce breaks on thaw.