Easy Green Bean Casserole Recipe From Scratch

I make this green bean casserole from scratch every Thanksgiving, and it beats any canned version I’ve tried. The creamy mushroom sauce takes 10 minutes on the stove. Crispy golden fried onions on top finish it in 25 more minutes of baking.

Why This Green Bean Casserole Works

The sauce starts with butter, mushrooms, and flour — a real roux that holds together and coats every green bean. Canned soup shortcuts give you a flat, salty base. This homemade version has a rich, savory depth that actually tastes like mushrooms.

Blanching the green beans first keeps them bright and tender-crisp. Skip this step and they come out limp and gray after baking. Two minutes in boiling water before they go in the dish is worth every second.

The fried onions go on in two rounds. Half bake into the casserole and soak up the sauce. The rest go on for the final 5 minutes so they stay crispy and golden on top.

Ingredients

• 1.5 lbs fresh green beans, trimmed and cut into 2-inch pieces
• 3 tablespoons unsalted butter
• 8 oz cremini mushrooms, sliced
• 3 cloves garlic, minced
• 3 tablespoons all-purpose flour
• 1.5 cups chicken broth
• 0.75 cup whole milk
• 0.5 teaspoon salt
• 0.25 teaspoon black pepper
• 1.5 cups French fried onions, divided

What You Need for Green Bean Casserole From Scratch

Fresh green beans — the texture holds up better than frozen or canned. If you only have frozen beans, thaw and pat them dry first to avoid a watery sauce.

Cremini mushrooms — earthier and meatier than white button mushrooms. Baby bella mushrooms are the same thing and work just as well.

Unsalted butter — controls the salt level since fried onions and broth already add plenty. Salted butter works but taste before adding the half teaspoon of salt.

All-purpose flour — thickens the sauce by absorbing liquid from the broth and milk. Cook it for 2 minutes after adding it or the casserole will taste floury.

Chicken broth — adds savory depth without cream. Low-sodium broth gives you more control over the final salt level.

Whole milk — makes the sauce creamy without being heavy. Half and half works too for a richer finish.

French fried onions — the crispy topping that defines this dish. Durkee or French’s both work. Add the second layer only in the final 5 minutes or they will steam and go soft.

How to Make Green Bean Casserole

1. Preheat oven to 375°F (190°C). Grease a 1.5-quart baking dish.
2. Blanch green beans in a large pot of boiling salted water for 5 minutes.
3. Drain and set aside.
4. Melt butter in a large skillet over medium heat.
5. Add sliced mushrooms. Cook for 5 minutes until softened and browned.
6. Add minced garlic. Cook for 1 minute until fragrant.
7. Sprinkle flour over the mushrooms. Stir to coat evenly. Cook for 2 minutes.
8. Pour in chicken broth gradually, whisking constantly until smooth.
9. Add milk. Stir and cook for 3 minutes until the sauce thickens.
10. Season with salt and black pepper. Remove from heat.
11. Fold in the blanched green beans until fully coated.
12. Transfer to the baking dish. Top with 1 cup of the fried onions.
13. Bake uncovered for 20 minutes until bubbling.
14. Scatter remaining 0.5 cup fried onions on top. Bake 5 more minutes until golden.

Green Bean Casserole Variations

Cheesy Green Bean Casserole

Stir 1 cup of shredded sharp cheddar into the sauce before adding the beans. The cheese melts into the mushroom roux and gives the casserole a golden, stretchy layer under the fried onions. Sharp cheddar has the most flavor impact here.

Slow Cooker Green Bean Casserole

Combine the sauce and blanched green beans in a slow cooker. Cook on low for 3 hours or high for 1.5 hours. Add the fried onions only in the last 15 minutes with the lid off so they toast rather than steam.

Gluten-Free Green Bean Casserole

Swap all-purpose flour for a 1:1 gluten-free flour blend in the same quantity. Use gluten-free fried onions — Trader Joe’s and Ian’s make them. The sauce texture is identical and you won’t taste a difference.

Vegan Green Bean Casserole

Use olive oil instead of butter, vegetable broth instead of chicken broth, and unsweetened oat milk instead of whole milk. Skip standard fried onions and use a vegan-certified brand. The sauce thickens the same way.

Tips for the Best Green Bean Casserole

• I always blanch the green beans before baking — raw beans stay tough through a 25-minute bake.
• Cook the flour for at least 2 minutes in the butter before adding liquid. This removes the raw flour taste.
• Use a wide, shallow baking dish so every bite gets crispy onion on top — deep narrow dishes trap steam and soften the topping.
• Let the casserole rest for 5 minutes after baking before serving. The sauce thickens as it cools slightly.
• Fresh green beans give the best texture, but frozen beans (thawed and patted dry) work in a pinch.
• If making ahead, assemble without the fried onions. Cover and refrigerate up to 24 hours. Add onions and bake as directed from cold — add 5 extra minutes.

Make Ahead & Storage

I assemble this green bean casserole the night before holiday meals — everything except the fried onion topping. Cover tightly with plastic wrap and refrigerate for up to 24 hours. Pull it out 30 minutes before baking to take the chill off.

Leftovers keep in the fridge for 3 days in an airtight container. Reheat in a 350°F (175°C) oven for 15 minutes to crisp up the onion topping. Microwaving works but the onions go soft. To freeze, cool completely, cover tightly, and freeze for up to 2 months without the onion topping — add fresh onions when you reheat.

Common Questions

Can I use canned green beans instead of fresh?

Yes, but drain and rinse them well first. Canned beans are already soft, so skip the blanching step entirely. The texture will be softer than fresh beans but the flavor is still good with the homemade mushroom sauce.

Why is my green bean casserole watery?

Two common causes: beans that weren’t fully drained after blanching, or sauce that wasn’t thick enough before baking. Let the sauce bubble and thicken on the stove for a full 3 minutes before folding in the beans.

Can I make green bean casserole without mushrooms?

Yes. Substitute 1 can of cream of mushroom soup diluted with 0.5 cup milk for the mushroom-roux sauce. The casserole will taste more like the classic version but still works with the fresh beans and homemade baking method.

How do I keep the fried onion topping crispy?

Add half the onions before baking and the remaining half only in the final 5 minutes. Keep the oven temperature at 375°F — lower temperatures cause steam to soften the topping before it can toast.

Can I double this recipe?

Yes. Use a 9×13-inch baking dish and double all ingredients. The bake time stays the same at 25 minutes total — the larger surface area compensates for the extra volume. Check that the sauce is bubbling before adding the final onion layer.

This easy green bean casserole from scratch is the one side dish I make every year without fail. Save this recipe and tap the link for the full recipe with all the steps.