Green Bean Casserole from Scratch

This Green Bean Casserole is made entirely from scratch – with a creamy homemade mushroom sauce, fresh or frozen green beans and plenty of fried onions! It’s sure to be the star of any holiday dinner.

I have to confess: I absolutely adore green bean casserole. And pretty much any vegetable smothered in creamy sauce and baked with a crunchy topping… It’s just so, so good.

Here we’re making a creamy mushroom sauce from scratch as the base of the casserole (no canned soups to be found!) and add crisp green beans and fried onions. You can either make your own fried onions or use classic French’s, whatever you prefer!

Ingredients you’ll need

Here is a visual overview of the ingredients in the recipe. Scroll down to the printable recipe card at the bottom of this post for quantities!

Ingredient notes

• Onions: I only had one small box of fried onions left, so I made my own but left the box in the photo above for easy recognition. You can use one 6-oz box for less onion, or two for more – or make your own for extra gold stars.
• Green beans: I use frozen, defrosted, drained green beans. If you’re using fresh, make sure to cook them first.
• Mushrooms: White cremini mushrooms are what I prefer here, but brown button are fine, too.
• Milk: Whole milk will absolutely work best here. I do not recommend using anything less than 2%.
• Broth: Chicken or vegetable are both fine. If you have vegetarians eating with you who often rely on the side dishes during holiday dinners, make sure to use vegetable broth.
• Worcestershire sauce: I always, always keep this on hand to season this kind of homey, hearty food. You can use soy sauce instead.

How to make green bean casserole from scratch

1. Start by cooking the mushrooms in butter. Once they are fully softened, stir in the garlic.

2. Sprinkle the flour over the mushrooms, then stir well. Add the milk and broth, stirring well to create a smooth sauce (keep the heat on medium-low for this, or you’ll end up with a lumpy, scorched dish).

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3. Once the sauce has thickened, take it off the heat and stir in the cheeses until melted.

4. Finally, stir in the defrosted green beans and about ¾ of a 6-oz box of fried onions.

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5. Transfer to a greased casserole dish (I recommend a shallow 9×11 inch dish for faster baking and less scorching of the onions). Top with onions, then bake until bubbly and golden brown.

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I highly recommend leaving this dish on the counter for no more than 5-10 minutes before serving, because that’s when it is the creamiest. So good!

Recipe tips

• Make sure you lower the heat before sprinkling the flour over the mushrooms, you do not want to burn it or your sauce will be ruined beyond repair.
• Likewise, make sure your pan is not too hot when you pour in the liquids, else the flour will seize up too quickly and yield a lumpy sauce.
• Frozen beans need to be fully defrosted, rinsed and drained/patted dry well. Otherwise they release too much water into the sauce.
• Fresh beans need to be blanched, drained and patted dry for the same reasons.
• I highly recommend placing the casserole on a rack in the lower part of your oven. This helps to keep the fried onions from scorching.

Make ahead and storage tips

Make ahead: When making the casserole ahead, I highly recommend blanching the frozen green beans first to reduce the risk of any food-borne illnesses developing over time. Then fully assemble the casserole, but do NOT add the fried onion topping.

Tightly wrap in plastic wrap and refrigerate for up to 3 days.

Remove the casserole from the fridge, unwrap and let sit on the counter as the oven heats up. Add the fried onion topping and bake as directed in the recipe, adding 5-10 extra minutes if needed. Again, it’s important for frozen vegetables to be fully cooked before consuming.

Leftovers: Allow the casserole to cool to room temperature, then wrap well and store in the fridge for up to 4 days. Thoroughly reheat before serving.

More classic holiday sides

PS If you try this recipe, please leave a review in the comment section and add a star rating in the recipe card – I appreciate your feedback! Follow along on Pinterest, Facebook or Instagram.

Printable recipe

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