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).
cook mushrooms stir in flour, then add liquids
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.
finish sauce with cheeses combine with green beans and some onions
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.
transfer to casserole dish sprinkle with fried onions and bake
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.
Green Bean Casserole from Scratch
Recipe details
Ingredients
- 4 tablespoons unsalted butter
- 12 ounces white button mushrooms sliced
- 2 cloves garlic minced
- ¼ cup all-purpose flour
- 2 cups milk whole milk preferred
- 1 cup broth chicken or vegetable
- 2 teaspoons Worcestershire sauce OR soy sauce
- ½ teaspoon ground black pepper
- ⅛ teaspoon ground nutmeg
- salt to taste
- ¼ cup grated parmesan cheese OR shredded cheddar
- 2 tablespoons cream cheese
- 2 (6-oz) cans French's Fried Onions or less to taste
- 2 (12-oz) bags frozen green beans defrosted, rinsed and drained/patted dry
Instructions
- Cook mushrooms: Melt butter in deep skillet over medium-high heat. Add mushrooms and cook until softened, about 5 minutes. Stir in garlic and cook for one more minute.
- Make sauce: Reduce heat to medium-low. Sprinkle flour evenly over mushroom mixture, stirring well for 1-2 minutes. Pour in milk and broth, stirring constantly to keep any lumps from forming. Stir in Worcestershire sauce, pepper and nutmeg. Season with salt to taste, then simmer until thickened, about 5 minutes, stirring often.
- Prep: As sauce is simmering, place a rack in the lower-middle part of the oven. Heat oven to 350°F.
- Finish assembly: Once thickened, remove gravy from heat. Stir in green beans and ½ – ¾ of ONE can of fried onions. Spread in shallow, greased 9×13-inch baking dish and top with fried onions to taste.
- Bake: Bake casserole until bubbly, 15-25 minutes (depending on size of dish; frozen beans must be fully heated through before serving!). Allow to sit on counter for 5-10 minutes, then serve immediately.
Notes
Ingredient notes
- 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.
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.
Janet says
Hi Nora, this recipe sounds super!! Will save this for xmas 2022! My daughter is vegetarian and I have been able to find vegetarian Worcestershire sauce. If not available, I use Tamari or soy sauce for that umami flavor, especially for vegan gravy.
Nora says
Janet, I hope you’ll enjoy it in a years’ time 🙂
Elese says
Hi! Going to use your recipe, but have a quick question…I need to travel an hour with it. Should I assemble and bake completely then reheat once I am at my destination? Should I leave off the onions then reheat? Help! Thanks!!
Nora says
Elese, if you have time at your destination to bake it, I would just assemble it without the onions on top and wrap it up, transport it this way (I would blanch the green beans before adding, in this case). Then add the onions and bake it once you’re there.