Green Bean Casserole

Michael Eisenwasser

Print Recipe

A scratch-sauce green bean casserole with a crispy leek-green topping. No canned soup, no fried onion strings.

Prep 20 min

Cook 30 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 soy sauce or tamari (gluten-free)

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

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. Fold in half the crispy leek greens; reserve the rest for the top.

Assemble and Bake

1. Heat the oven to 375°F (190°C). Butter a 3-quart (9x13-inch) baking dish.
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 reserved crispy leek greens over the hot casserole and serve.

Tips & Substitutions

• Do not use canned cream-of-mushroom soup. Most brands contain mushroom, 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 high-FODMAP for two reasons: onions are high in fructans, and the coating is wheat flour. Crispy leek greens and gluten-free breadcrumbs give you the crunch and the onion flavor instead.
• Leek greens only, not whites. Monash rates the green tops as low-FODMAP at a 2/3 cup serve; the white bulb is high-FODMAP like an onion. Trim where the stalk turns dark green and save the whites for stock.
• 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 in a pinch (thaw and pat very dry). Avoid canned green beans; they turn to mush under 20 minutes in the oven.
• Make ahead. Blanch the beans and make the sauce a day ahead and refrigerate separately. Crisp the leek greens and toss the breadcrumb topping the day of. Assemble and bake straight from the fridge, adding 5 to 7 minutes to the bake time.

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.

Heavy cream has less lactose than milk. The fat displaces the water that lactose rides in. Monash rates 1/2 cup (125 ml) per serve as low-FODMAP. An eighth of this casserole works out to about 2 tablespoons of cream per serving, well under the limit.

Lactose-free milk and a scratch roux replace the can. Canned cream-of-mushroom soup contains mushroom, 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. Fructans, the FODMAP in garlic, dissolve in water but not in oil. Steeping garlic in hot oil and then straining pulls the flavor into the fat and leaves the fructans behind. That's why garlic-infused oil stands in for minced garlic on a low-FODMAP diet.

Soy sauce adds a savory bottom note. A small pour of soy sauce or tamari adds umami that covers for the missing onion and mushroom depth. Monash rates 2 tablespoons of soy sauce as low-FODMAP; this recipe uses 2 teaspoons across 8 servings, well under the limit.

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. Green bean casserole doesn't freeze well — the beans go limp and the cream sauce breaks on thaw. Plan to eat it within a few days, which is part of why it shows up on the Thanksgiving table and not in the freezer.

Not sure about an ingredient? FODMAP Tracker includes a database of 1,000+ foods with FODMAP ratings to help you cook with confidence.