Green Bean Casserole with Creamy Mushroom Sauce and Fried Onions

Green bean casserole is a familiar American side dish, especially at holiday tables, where tender green beans are served in a savoury mushroom cream sauce beneath a crisp onion topping. This version keeps the dish straightforward and fresh-tasting: the beans are briefly boiled so they stay bright and just tender, while the mushrooms are cooked until lightly golden to deepen the sauce’s flavour. Double cream and whole milk give a rich but spoonable texture, and the fried onions added at the end bring the recognisable crunch that makes the casserole so satisfying alongside roast meats, vegetarian mains or a larger spread.
Cuisine style American comfort food
Cooking style Make-ahead friendly • Crowd-friendly
Time commitment Under 1 hour

Why this recipe works

  • Deeper mushroom flavour: Cooking the mushrooms until their moisture evaporates concentrates their savoury flavour before the cream and milk are added.
  • Creamy centre, crisp topping: Tender green beans sit in a rich mushroom sauce, while fried onions added at the end keep the top crisp and golden.
  • Straightforward method: The recipe uses simple steps: blanch the beans, simmer the sauce, combine, bake and finish with the topping.

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Timing notes

  • Let it stand before serving: A short rest after baking helps the sauce settle slightly, so the casserole serves more neatly.
  • Best served hot: Serve soon after the fried onions are crisped, as the topping will soften if left sitting for too long.

Make-ahead tips

  • Prepare the base in advance: The beans and mushroom sauce can be assembled ahead and chilled before baking. Add the fried onions only for the final bake.
  • Reheat for best texture: Reheat in a 180°C (355°F) oven until piping hot, then refresh the top with extra fried onion if needed.

Ingredient notes

  • Green beans: Blanching the beans first keeps them bright and just tender before they finish cooking in the oven.
  • Mushrooms: Button mushrooms give a mild, classic flavour; oyster mushrooms can be used for a more pronounced savoury note.
  • Fried onions: Adding the onions near the end protects their crunch and prevents them from becoming heavy or soggy.

Authenticity notes

  • American home-style side: Green bean casserole is a recognisable American side dish, often served from the baking dish as part of a larger meal.
  • Fresh mushroom sauce: This version keeps the familiar creamy profile and fried onion topping while using a freshly cooked mushroom sauce.

Equipment you'll need

Ingredients
Instructions
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  1. Heat the oven to 190°C (375°F). Bring a large pot of well-salted water to the boil.
  2. Trim the green beans, then boil for 4 to 5 minutes until bright green and just tender. Drain well in a colander and set aside.
  3. Slice the button mushrooms and finely chop the garlic. Melt the unsalted butter in a large frying pan over medium-high heat.
  4. Add the mushrooms and cook for 6 to 8 minutes, stirring, until their liquid has evaporated and they are lightly golden. Stir in the garlic and cook for 30 seconds until fragrant.
  5. Pour in the whole milk and double cream, then season with the fine sea salt and black pepper. Bring to a gentle simmer and cook for 4 to 6 minutes, stirring, until the sauce lightly coats the back of a spoon.
  6. Add the drained green beans to the pan and toss to coat in the creamy mushroom sauce. Tip into a baking dish and spread into an even layer.
  7. Bake for 18 to 22 minutes until bubbling around the edges. Scatter the fried onion over the top and bake for 5 minutes more until the topping is crisp and golden.
  8. Rest for 5 minutes so the sauce settles slightly, then serve hot. Add a little extra black pepper at the table if you like.

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Recipe notes

Tips

  • Drain the green beans very well so the sauce stays creamy rather than watery.
  • Cook the mushrooms until their moisture has evaporated and they start to colour; this gives the casserole a deeper savoury flavour.
  • If serving vulnerable groups, make sure the casserole is baked until piping hot all the way through.

Substitutions

  • Replace double cream with whole milk for a lighter sauce, but simmer a little longer so it thickens.
  • Replace button mushrooms with oyster mushrooms for a more pronounced mushroom flavour.

Storage

  • Refrigerate up to 3 days
  • Cool completely, then refrigerate in a sealed container. Reheat in a 180°C (355°F) oven for 15 to 20 minutes until piping hot; add a fresh sprinkle of fried onion for best crunch.

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Green Bean Casserole with Creamy Mushroom Sauce and Fried Onions
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Recipe overview

  • Servings: 4 servings
  • Total time: 50min (20min active)
  • Difficulty: Easy
  • Cuisine: American
  • Allergens:
    Milk
Beginner friendly Kid friendly

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