Green Bean Casserole with Crispy Fried Onions

Step 1: Boil the green beans for 3 minutes, until just tender or cooked to your taste. Drain and rinse under cold water to stop them cooking further. You can also steam the beans.

Step 2: Transfer the beans to a clean tea towel and pat dry. Set aside.

Step 3: Line a tray with 3–4 layers of paper towels.

Step 4: Toss the onions with the flour, panko, salt and pepper.

Step 5: Pour about 2 cm (3/4 inch) of oil into a heavy-based skillet and heat over medium-high heat. Dip the end of one onion into the oil; it should sizzle immediately.

Step 6: Add a small batch of onions to the oil and fry for 1 1/2 minutes, or until light golden brown.

Tip: Avoid crowding the skillet.

Step 7: Transfer the onions to the prepared tray and spread them out rather than piling them up.

Step 8: Repeat with the remaining onions in 5–6 batches. Leave them uncovered to cool.

Step 9: Melt the butter in a skillet over medium-high heat. Add the mushrooms and cook for 1 minute.

Step 10: Add the salt and pepper. Cook until the mushrooms start to soften, about 1 1/2 minutes, then add the garlic and cook for 1 minute, until golden.

Step 11: Reduce the heat to medium, add the flour and mix until no flour is visible.

Step 12: Stir constantly as you gradually pour in half the broth. Once the flour lumps have dissolved, pour in the remaining broth and the cream, then stir.

Step 13: Add the nutmeg and stir.

Step 14: Cook for 5 minutes, stirring occasionally at first and then regularly as the sauce thickens. It is ready when it thickly coats the back of a wooden spoon and you can draw a path through it. The sauce will not thicken further in the oven.

Step 15: Preheat the oven to 350°F / 180°C (160°C fan).

Step 16: Return the beans to the pot they were boiled in, or use a bowl. Pour the mushroom sauce over them and stir.

Step 17: Transfer the mixture to a 2.5-quart / 2.5-litre casserole dish and smooth the surface.

Step 18: Sprinkle the onions over the top; you may not need all of them. Bake for 15 minutes, until bubbling at the edges and the onions are deep golden. Check after 10 minutes to make sure the onions are not burning.

Step 19: Serve immediately.