Ingredients

750g / 1.5lb green beans, trimmed and halved

2 large yellow onions, peeled, halved, and thinly sliced (or 3 medium)

1/4 cup (35g) plain/all-purpose flour

2 tbsp panko breadcrumbs

1/2 tsp salt

1/4 tsp black pepper

4 cups / 1 litre vegetable oil (or peanut, canola oil) for deep-frying

3 tbsp (50g) unsalted butter

360g / 12 oz mushrooms, chopped into 1cm / 1/3″ pieces

3/4 tsp salt

1/4 tsp black pepper

2 garlic cloves, minced

3 tbsp (35g) plain/all-purpose flour

1 1/2 cups (375ml) vegetable or chicken broth/stock, low sodium

1/2 cup (125ml) heavy/thickened cream

Pinch of nutmeg (or freshly grated)

Instructions

Step 1: Boil the green beans for 3 minutes until just tender or to your taste. Drain them and rinse under cold tap water to stop the cooking process. Alternatively, you can steam the beans. Transfer to a clean tea towel and pat dry. Set aside.

Step 2: Prepare the crispy onions by lining a tray with 3 to 4 layers of paper towels. Toss the sliced onions with flour, panko breadcrumbs, salt, and pepper.

Step 3: Heat about 2cm (3/4″) of oil in a heavy-based skillet over medium-high heat. Test the oil by dipping the end of one onion strip in—it should sizzle immediately.

Step 4: Fry onions in small batches (5-6 batches) for about 1 1/2 minutes or until lightly golden brown. Avoid overcrowding in the skillet. Transfer fried onions to the paper towel-lined tray, spreading them out to cool without piling. Set aside.

Step 5: For the creamy mushroom sauce, melt butter in a skillet over medium-high heat. Add chopped mushrooms and cook for 1 minute.

Step 6: Season with salt and pepper. Cook until mushrooms soften, about 1 1/2 minutes, then add minced garlic and cook for another minute until garlic is golden.

Step 7: Reduce heat to medium. Stir in flour and mix well until it is fully absorbed.

Step 8: Gradually pour in half the broth while stirring constantly to avoid lumps. Once smooth, add the remaining broth and cream. Stir in a pinch of nutmeg.

Step 9: Cook for 5 minutes, stirring occasionally at first and more regularly as the sauce thickens. It should coat the back of a wooden spoon and a clear path can be drawn through it. Note that the sauce will thicken more in the oven.

Step 10: Preheat your oven to 350°F / 180°C (160°C fan).

Step 11: Return the cooked green beans to the pot or a mixing bowl. Pour the mushroom sauce over the beans and stir to combine.

Step 12: Transfer the mixture to a 2.5-quart (2.5-liter) casserole dish and smooth the surface.

Step 13: Sprinkle the crispy onions evenly on top (you may not use them all). Bake for 15 minutes, checking at 10 minutes to ensure onions are not burning, until the edges are bubbling and the onion topping is deep golden.

Step 14: Serve immediately and enjoy!

Tips & Variations

For extra flavor, add a splash of soy sauce or Worcestershire sauce to the mushroom sauce.

Use fresh mushrooms for best results, but canned mushrooms can be a shortcut if pressed for time.

You can make the crispy onions ahead and store them in an airtight container to keep them crunchy.

Vegetarian option: Use vegetable broth and skip any animal-based ingredients.

FAQs

Can I use frozen green beans for this recipe?

Yes, frozen green beans can be used. Thaw them thoroughly and pat dry before boiling or steaming to avoid excess moisture in the casserole.

How can I make this dish ahead of time?

You can prepare the casserole mixture and keep it refrigerated, then add the crispy onions just before baking. Alternatively, bake the casserole without the onions and add them fresh after baking for best texture.