Homemade Green Bean Casserole (from Scratch!)

Ingredients

• 1yellow onion, thinly sliced
• 1red onion, thinly sliced
• 600 ml (2½ cups)buttermilk
• 190 g (1½ cups)plain flour
• 60 g (1 cup)panko breadcrumbs
• ½ tsp eachsalt and pepper
• for fryingvegetable or rapeseed oil
• 794 g (1¾ lb; 28 oz)green beans, trimmed and halved
• 42 g (3 tbsp)unsalted butter
• 30 ml (2 tbsp)olive oil
• 340 g (12 oz)cremini mushrooms, sliced 6 mm thick
• 4 clovesgarlic, minced
• 1 tspsalt
• 43 g (⅓ cup)plain flour
• 710 ml (3 cups)low-sodium chicken stock
• 120 ml (½ cup)double cream
• 1½ tspDijon mustard
• 1½ tspWorcestershire sauce
• 1 tsp eachdried thyme and dried parsley
• ½ tsppepper
• ¼ tsp eachdried oregano and nutmeg
• 56 g (½ cup)freshly grated Cheddar
• 25 g (¼ cup)freshly grated Parmesan
• 120 ml (½ cup)soured cream

Instructions

1. 1

   Soak the onions

   Put the sliced yellow and red onions in a shallow dish and pour over the buttermilk. Press them down to submerge them as much as possible and leave at room temperature for 1 hour, stirring and pressing them down occasionally. Cover and refrigerate if soaking for longer.

2. 2

   Heat the oil

   When ready to fry, pour oil into a Dutch oven or other heavy, deep pot to a depth of about 5 cm. Heat it to 190°C.

3. 3

   Prepare the coating

   While the oil heats, mix the flour, panko, ½ tsp salt and ½ tsp pepper in a large bowl. Set out a large baking tray lined with kitchen paper.

4. 4

   Coat the onions

   Test the oil with a small pinch of panko; it is ready when the crumbs bubble and fry. Use tongs to lift a handful of onions from the buttermilk into the flour mixture. Toss to coat, shake off excess and carefully transfer to the oil.

5. 5

   Fry until golden

   Fry the onions for 1–2 minutes, watching closely, until lightly golden; they will darken further in the oven. Lift them out with a heatproof slotted spoon or tongs and drain on the kitchen paper. Repeat with the remaining onions.

6. 6

   Blanch the beans

   Bring a large pot of water to the boil and stir in 2 tbsp salt. Add the green beans and blanch for 5 minutes, starting the timer as soon as they go in. Meanwhile, prepare a large bowl of iced water. Transfer the beans to it with a slotted spoon to stop the cooking, then drain and set aside.

7. 7

   Cook the mushrooms

   Melt the butter with the olive oil in a Dutch oven or large pot over medium heat. Add the mushrooms and cook for 3–5 minutes, until nicely browned and beginning to soften. Add 1 tsp salt and the garlic, then sauté for 30 seconds.

8. 8

   Start the sauce

   Whisk in the flour and cook for 1 minute, stirring. Reduce the heat to low and gradually whisk in the chicken stock and cream, followed by the Dijon, Worcestershire sauce and all the listed seasonings.

9. 9

   Thicken the sauce

   Bring the sauce to the boil while whisking constantly. Lower it to a simmer and cook for about 5 minutes, whisking often, until thickened.

10. 10

    Add the cheese

    Take the pot off the heat. Whisk in the Cheddar until melted, then the Parmesan until melted, and finally the soured cream until blended.

11. 11

    Combine the beans

    Pat the green beans dry and stir them into the sauce. Mix in 1½ cups of the fried onions. Add extra chicken stock if needed to thin the sauce.

12. 12

    Bake the casserole

    Transfer the mixture to a lightly greased 23 x 33 cm baking dish and scatter over as many of the remaining onions as you like. Bake at 180°C for 15–20 minutes, until hot and bubbling.

What is green bean casserole?

Green bean casserole is an American baked side dish, especially familiar at holiday meals. This from-scratch version brings blanched beans together with a mushroom cream sauce and a crisp onion topping.

Fresh beans keep their shape, while mushrooms, stock, cream and cheese make the sauce savoury and rich. The homemade fried onions give the top a crunchy finish.

Nutrition and macros by portion

The nutrition label shows one serving as written: 470 calories, 12g protein, 42g carbs, 28g fat.

The green beans and flour provide most of the carbohydrates, while the frying oil, butter, cream, cheeses and soured cream contribute much of the fat. The beans, mushrooms, dairy and chicken stock provide some protein. Serve it with a lean protein and another vegetable or salad for a more balanced plate.

Why blanch the beans first?

Blanching: Boil the beans for 5 minutes, then move them straight into iced water. This stops them cooking further before they go into the sauce and oven.

Drying: Drain the beans and pat them dry before mixing them in. Excess water can loosen the sauce.

Building the mushroom sauce

Browned mushrooms: Give them 3–5 minutes in the butter and oil so they soften and take on colour before you add the garlic.

Flour and stock: Stir the flour for 1 minute, then add the stock and cream gradually while whisking. This helps the sauce thicken smoothly as it simmers.

Getting crisp fried onions

Coating: Let excess buttermilk drip off and shake away loose flour and panko before frying. Work in handfuls so the onions are easier to handle.

Colour: Fry for just 1–2 minutes, until lightly golden. They continue to brown in the oven, so remove them before they become dark.

The right texture and timing

Sauce: After about 5 minutes at a simmer, it should be thick enough to cling to the beans while still easy to stir. Whisk often to keep it smooth.

Bake: The casserole needs 15–20 minutes at 180°C, just until hot and bubbling. The onions are already fried, so the bake is for heating the dish through and crisping the topping.

Making it ahead

You can prepare the onions and sauce, blanch the beans and assemble the casserole in advance. Keep the fried onions separate so they stay crisp, and refrigerate the assembled dish.

Add the onions before baking. If the casserole is cold from the fridge, allow extra time in the oven and check that it is hot and bubbling in the centre.

What to serve with it

This rich casserole works alongside roast turkey, chicken or another simple main, with potatoes and a fresh salad or other vegetables to round out the plate.

Because the sauce and onions are creamy and savoury, plainer sides help balance the meal without competing with them.

Recipe notes & tips

• Use a thermometer if available to bring the frying oil to 190°C before adding the onions.
• Fry the onions in batches so they have room to cook evenly.
• Keep the beans in the iced water only until they have cooled, then drain them well.
• Grate the Cheddar and Parmesan fresh so they melt readily into the sauce.
• Add the fried onions just before baking if you have assembled the casserole ahead.
• Use a slotted spoon to lift the beans from the boiling water without pouring out the pot.

Variations

• Use vegetable stock: Swap it for the chicken stock for a meat-free version.
• Change the cheese: Use another good-melting cheese in place of the Cheddar.
• Add sliced almonds: Scatter them over the onion topping for extra crunch.
• Make it milder: Leave out the Dijon mustard for a gentler sauce.
• Use frozen beans: Thaw them and drain well before stirring them into the sauce.

Common mistakes to avoid

• Overfrying the onions: They darken in the oven, so remove them when only lightly golden.
• Adding wet beans: Drain and pat them dry so they do not water down the sauce.
• Lumpy sauce: Whisk the stock and cream in gradually after stirring the flour into the mushrooms.
• Skipping the ice bath: Cool the blanched beans promptly to stop them cooking further.
• Crowding the frying pot: Cook the onions in batches to maintain the oil temperature.
• Baking too long: Take the casserole out once it is hot and bubbling to avoid overcooking the beans.

How to store

Refrigerate leftovers in a covered container for up to 3 days. Reheat in an oven at 180°C until hot throughout; the onion topping may soften after storage. For best texture, store any extra fried onions separately and add them after reheating.

Frequently asked questions