How to Make Green Bean Casserole

published Nov 12, 2023
Green Bean Casserole Recipe

Learn how to make the classic Thanksgiving side with fresh or canned green beans, a homemade mushroom cream sauce, and store-bought crispy onions.

Serves6 to 8

Prep10 minutes to 20 minutes

Cook45 minutes to 55 minutes

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Close up view of the corner of the casserole with a scoop missing.
Credit: Photo: Vicky Wasik ; Food Stylist: Rachel Perlmutter

Classic Thanksgiving recipes tug at such a tender spot in our memories. It isn’t until the dish is on the table that we end up wishing it was just better. Green bean casserole is a prime example of a classic dish that can be improved upon, while honoring the nostalgic hold it has on us. 

Green bean casserole is composed of three separate elements: the green beans, the mushroom cream sauce, and the crispy onion topping. The decision is yours when it comes to canned or fresh green beans — it’s really a matter of convenience and textural preference. Homemade mushroom cream sauce and those store-bought crispy onions are a must here, so I won’t try to convince you otherwise. Here’s how to put it all together to make the best classic green bean casserole.

What Ingredients Are in Green Bean Casserole?

  • Green beans: Blanch fresh green beans for a crisp-tender green bean texture or opt for three (about 15-ounce) cans of green beans for a softer bite. 
  • Mushrooms: Browning sliced white button mushrooms in butter gives the creamy sauce its umami flavor. Substitute with baby portobello (cremini) mushrooms for an even deeper flavor.
  • Butter: Use unsalted butter for browning the mushrooms and garlic, and to toast the flour for thickening the sauce.
  • All-purpose flour: Cook the flour in butter as insurance against a lumpy gravy. Wait until it turns golden and smells toasty before adding the liquids.
  • Chicken or vegetable broth: Low-sodium broth is best for controlling the seasoning level (especially if you’re using canned green beans). It’s easy to keep the dish vegetarian by using low-sodium vegetable broth
  • Milk: With so many rich dishes on the table, there’s no need for heavy cream here. Instead, opt for whole or 2% milk to give the mushroom sauce its creamy flavor. 
  • Crispy fried onions: There’s no substitute for the classic crunch of store-bought crispy fried onions. One small (2.8-ounce) container is enough to cover the casserole.

Why Is My Green Bean Casserole Soggy?

Your mushroom cream sauce may be too thin if you have added more broth or milk than called for, if you have not simmered the sauce long enough, or if it was not cooked on the specified heat level. Luckily, this is an easy fix. Place the skillet with the sauce over medium-high heat and whisk frequently as it comes to a rapid boil. Continue whisking until the mixture “coats the back of a spoon.” This means if you dip a spoon into the sauce, you should be able to draw your finger through the sauce and a clean line should appear. If the sauce runs together, keep cooking until you’re able to do so.  

How to Make Green Bean Casserole in Advance

It’s simple to prepare this classic green bean casserole in advance, whether you’re getting ready for the week ahead or are in the midst of holiday preparations. Assemble the casserole, but leave off the crispy onion topping. Cover and refrigerate the casserole for up to one day. Remove the casserole from the refrigerator while the oven heats. Sprinkle with the crispy onions, then bake, adding an additional 15 to 20 minutes to the original bake time. Make sure to check the onions towards the end of cooking, as you may need to cover with foil to prevent over-browning.

Green Bean Casserole Recipe

Learn how to make the classic Thanksgiving side with fresh or canned green beans, a homemade mushroom cream sauce, and store-bought crispy onions.

Prep time 10 minutes to 20 minutes

Cook time 45 minutes to 55 minutes

Serves 6 to 8

Nutritional Info


  • 1 1/2 pounds

    fresh green beans

  • 8 ounces

    white button mushrooms

  • 2

    cloves garlic

  • 4 tablespoons

    (1/2 stick) unsalted butter, plus more for the baking dish

  • 1 1/4 teaspoons

    kosher salt, plus more for blanching and as needed

  • 1/2 teaspoon

    freshly ground black pepper

  • 1/4 cup

    all-purpose flour

  • 1 cup

    low-sodium chicken or vegetable broth

  • 1 1/2 cups

    whole or 2% milk, or half-and-half

  • 1

    (2.8-ounce) container fried onions (about 1 1/2 cups), such as French’s Fried Onions


  1. Bring a large pot of salted water to a boil over high heat. Meanwhile, prepare an ice bath by filling a large bowl halfway with ice and water. Arrange a rack in the middle of the oven and heat the oven to 350°F. Lightly coat a 9x13-inch or other 3-quart baking dish with unsalted butter.

  2. Trim the ends and cut 1 1/2 pounds green beans in half. Thinly slice 8 ounces white button mushrooms, halving first if the mushrooms are larger than 1 1/2-inches in diameter. Mince 2 garlic cloves.

  3. Add the green beans to the boiling water and cook until crisp-tender, about 4 minutes. Drain and transfer to the ice bath to stop the cooking. When cool, drain again and let sit in the colander while you make the sauce.

  4. Melt 4 tablespoons unsalted butter in a large skillet over medium-high heat. Add the mushrooms, 1 1/4 teaspoons kosher salt, and 1/2 teaspoon black pepper. Cook until the moisture is released and the mushrooms begin to brown, 5 to 7 minutes. Add the garlic and cook until fragrant, about 1 minute.

  5. Sprinkle 1/4 cup all-purpose flour evenly over the mushroom mixture and stir to combine. Cook until the flour is no longer dry and the film on the bottom of the pan turns golden, about 1 minute. Slowly whisk in 1 cup low-sodium chicken or vegetable broth, scraping the bottom of the pan.

  6. Add 1 1/2 cups whole or 2% milk, or half-and-half, and whisk to combine. Bring to a boil. Cook, whisking frequently, until the sauce thickens, 2 to 3 minutes. Remove the pan from the heat. Taste and season with more kosher salt as needed.

  7. Add the green beans and toss to coat in the sauce. Transfer the mixture to the baking dish, and spread into an even layer. (Alternatively, leave the mixture in the skillet if it is ovenproof, spread it into an even layer, and bake directly in the skillet.) Sprinkle evenly with 1 (2.8-ounce) container fried onions. Bake until the edges are bubbling and the onions are browned, 15 to 20 minutes.

Recipe Notes

Make ahead: Assemble the casserole without the onion topping, cover, and refrigerate up to 1 day ahead. Let the casserole sit at room temperature while the oven heats. Uncover and top with the fried onions. Bake for 30 to 40 minutes, covering the top with aluminum foil in the final 10 minutes if the onions brown too quickly.

Substitutions: 3 (about 15-ounce) cans green beans can be substituted for the fresh green beans. Drain well before adding to the mushroom sauce.

Storage: Leftovers can be refrigerated in an airtight container for up to 4 days.