Green Bean Casserole is the ultimate comfort dish, blending creamy, savory, and crunchy textures in every bite. Tender green beans are enveloped in a rich, velvety sauce, topped with golden, crispy fried onions for a satisfying contrast. This classic recipe brings warmth to any table, perfect for cozy family dinners or festive gatherings. With just 20 minutes of prep and an hour in the oven, it’s as easy as it is delicious.
The flavors meld beautifully as it bakes, creating a dish that’s both hearty and nostalgic. Each forkful offers a harmonious mix of earthy beans, creamy sauce, and a hint of umami from the onions. Whether it’s a holiday centerpiece or a weeknight treat, this casserole never fails to impress. In just 1 hour and 20 minutes, you’ll have a crowd-pleaser that’s as comforting as it is flavorful.
What You’ll Need for Green Bean Casserole?
- 1½ pounds green beans, trimmed and halved
- 2 tablespoons extra-virgin olive oil
- 16 ounces cremini mushrooms, sliced (or substitute with white mushrooms)
- 2 tablespoons tamari (or substitute with soy sauce)
- 4 garlic cloves, minced
- 2 tablespoons fresh thyme leaves (or 2 teaspoons dried thyme)
- ¼ cup all-purpose flour
- 3 cups milk (any kind: whole, skim, or plant-based)
- 1½ teaspoons Dijon mustard
- ½ cup grated Parmesan cheese, plus more for sprinkling
- ¼ teaspoon freshly ground black pepper
- 1½ cups French fried onions (or homemade Crispy Baked Onions—see recipe notes)
How to Make Green Bean Casserole
- Preheat the oven to 400°F. Lightly grease a 9×13-inch baking dish.
- Blanch the green beans: Bring a large pot of salted water to a boil and prepare a bowl of ice water. Add the green beans to the boiling water and cook for 4 minutes. Drain and immediately transfer to the ice water to stop the cooking process. Drain again and dry on a towel.
- Cook the mushrooms: Heat the olive oil in a large skillet over medium heat. Add the mushrooms and cook until soft, 8 to 10 minutes. Stir in the tamari, garlic, and thyme.
- Make the sauce: Sprinkle the flour over the mushrooms and stir to coat. Add the milk and mustard, stirring to combine. Simmer, whisking often, until thickened, 15 to 20 minutes. Stir in the Parmesan cheese and pepper.
- Assemble the casserole: Spread ⅓ of the sauce into the prepared baking dish. Layer the green beans on top, then cover with the remaining sauce. Sprinkle the French fried onions evenly over the top.
- Bake: Cover the dish with foil and bake for 10 minutes. Uncover and bake for another 10 minutes. If the onions start to brown too much, cover the dish again for the remaining baking time.
- Garnish and serve: Sprinkle with additional Parmesan cheese, if desired. Serve hot and enjoy!
Perfect Pairings: Serving Suggestions
This Green Bean Casserole is a versatile side dish that pairs beautifully with roasted turkey, baked ham, or grilled chicken. For a complete holiday meal, serve it alongside mashed potatoes, cranberry sauce, and a fresh garden salad. Don’t forget a crusty loaf of bread to soak up any extra sauce!
Make It Your Own: Recipe Variations
Switch things up by using almond milk or oat milk for a dairy-free version. Add a kick of heat with a pinch of red pepper flakes or swap the cremini mushrooms for shiitake or portobello. For a crunchier topping, try mixing panko breadcrumbs with the fried onions before baking.
Save Time: Quick Prep Tips
To streamline prep, use pre-trimmed green beans and pre-sliced mushrooms. You can also make the sauce a day ahead and store it in the fridge—just reheat gently before assembling the casserole. If you’re short on time, skip the blanching step and use frozen green beans instead.
Keep It Fresh: Storage and Reheating
Store leftovers in an airtight container in the fridge for up to 3 days. Reheat in the oven at 350°F for 15-20 minutes to maintain the crispy topping. For a quick fix, microwave individual portions for 1-2 minutes, though the onions may lose some crunch.
Pro Tips: Equipment Guidance
A large skillet with high sides is ideal for making the sauce, as it prevents splatters and allows for easy stirring. Use a 9×13-inch baking dish with a lid or foil to cover during baking. A whisk is essential for achieving a smooth, lump-free sauce.
Green Bean Casserole
Ingredients
- 1½ pounds green beans, trimmed and halved
- 2 tablespoons extra-virgin olive oil
- 16 ounces cremini mushrooms, sliced
- 2 tablespoons tamari
- 4 cloves garlic, minced
- 2 tablespoons fresh thyme leaves
- ¼ cup all-purpose flour
- 3 cups milk, any kind
- 1½ teaspoons Dijon mustard
- ½ cup grated Parmesan cheese, plus more for sprinkling
- ¼ teaspoon freshly ground black pepper
- 1½ cups French fried onions, or homemade Crispy Baked Onions (see recipe notes)
Instructions
- Preheat the oven to 400°F. Lightly grease a 9×13-inch baking dish.
- Bring a large pot of salted water to a boil and set a large bowl of ice water nearby. Drop the green beans into the boiling water and blanch for 4 minutes. Drain, and immediately immerse in the ice water to stop the cooking process. Drain, and transfer to a towel to dry.
- Heat the olive oil in a large skillet, add the mushrooms, and cook until soft, 8 to 10 minutes. Stir in the tamari, garlic, and thyme. Sprinkle the flour over the mushrooms and stir again. Add the milk and mustard and stir to combine. Simmer until thickened, whisking often, 15 to 20 minutes. Stir in the Parmesan cheese and pepper.
- Spread ⅓ of the sauce into the baking dish. Layer with green beans and top with the remaining sauce. Sprinkle the onions on top and bake, covered, for 10 minutes. Uncover and bake 10 more minutes. If the onions start to brown too much, cover the dish for the remainder of the baking time. Garnish with sprinkles of Parmesan, if desired. Serve hot.