Can I assemble green bean casserole the day before Thanksgiving?

Yes, and the flavor improves for it. Blanch the beans, make the sauce, combine them and refrigerate the unbaked dish, tightly covered, for up to 24 hours. Keep the fried shallots separate at room temperature and add them after baking, or the topping will soften overnight.

Can I use frozen green beans instead of fresh in this casserole?

Yes. Skip the blanching, thaw the beans completely, and dry them very well in a clean towel, since frozen beans release extra water that can thin the sauce. Add about 2 minutes to the baking time and expect a slightly softer texture than fresh beans give.

Why is my mushroom sauce thin and watery?

Usually the beans went in wet or the sauce never reached a proper simmer. Dry blanched beans on a towel before folding them in, and let the sauce simmer until it thickly coats a spoon; it should ribbon, not pour. A few extra minutes of resting after baking also firms the dish.

How do I keep the crispy shallots from going soggy?

Fry them in small batches, drain them in a single layer, and store them uncovered at room temperature, never in the fridge. Most importantly, scatter them over the casserole after it rests, ideally at the table, so they never sit in the steam of the hot sauce.

Can this green bean casserole be made dairy-free?

Yes, with two straight swaps: olive oil for the butter and unsweetened oat milk for the half-and-half, in the same amounts. Brown the mushrooms well, since they carry the savory depth, and season the sauce confidently; the shallot topping is already dairy-free.

Green Bean Casserole From Scratch: Best 8 Servings

Ingredients

Scale

2 pounds fresh green beans, trimmed and cut in half
1 tablespoon fine sea salt, for the blanching water
3 large shallots, sliced into thin rings (for the topping)
3 tablespoons all-purpose flour (for the shallots)
1/2 teaspoon fine sea salt (for the shallots)
3 tablespoons neutral oil, for frying
2 tablespoons unsalted butter
12 ounces cremini mushrooms, sliced 1/4 inch thick
1 small yellow onion, finely diced
3 garlic cloves, minced
1 teaspoon fresh thyme leaves (or 1/2 teaspoon dried)
3 tablespoons all-purpose flour (for the sauce)
1 cup low-sodium chicken or vegetable broth
1 cup half-and-half
1 teaspoon soy sauce
1 teaspoon fresh lemon juice
3/4 teaspoon fine sea salt
1/2 teaspoon black pepper
1 pinch of ground nutmeg

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Instructions

Blanch the beans in well-salted boiling water for 4 minutes, until bright green and crisp-tender. Move to an ice bath, drain, and dry thoroughly on a towel.
Toss the shallot rings with the flour and salt. Fry in hot oil in two batches, 3 to 4 minutes per batch, until deep golden. Drain on paper towels and salt lightly.
Melt the butter in the same skillet and brown the mushrooms in two batches, undisturbed 2 minutes per side, until deeply golden.
Add the diced onion and cook 3 minutes. Stir in the garlic and thyme for 30 seconds.
Sprinkle in the flour and stir 1 minute. Whisk in the broth, then the half-and-half, and simmer 4 to 5 minutes until the sauce thickly coats a spoon.
Season with the soy sauce, lemon juice, salt, pepper and nutmeg. Taste and adjust; the sauce should be well seasoned on its own.
Heat the oven to 375°F (190°C). Fold the dry beans through the sauce and scrape into a buttered 9 by 13 inch dish.
Bake 18 to 20 minutes, until bubbling at the edges. Rest 5 minutes so the sauce turns glossy.
Scatter the crispy shallots over the top at the table and serve immediately.

Author: Chef Rita
Prep Time: 25 minutes
Cook Time: 35 minutes