How do I cook green beans so they stay squeaky?

Green beans have a narrow window. Undercooked they taste raw and grassy; a minute past their point they lose their colour and go floppy. Blanching and refreshing turns that narrow window into something you can hit reliably, and it can be done hours in advance.

Step by step

1. Top them, but leave the tails.The stem end needs trimming. The wispy tail is edible and looks better left on. Snap or cut a handful at a time by lining them up on the board.
2. Use a big pan of heavily salted water at a rolling boil.Far more water than you think, at a genuine rolling boil, salted to about 15 g per litre — more than for pasta. Volume means the temperature does not crash when the beans go in, and a hard boil cooks them fast enough to keep the colour.
3. Leave the lid off.The acids the beans release escape as steam. A lid sends them back into the water and turns the beans olive.
4. Cook three to five minutes and test by biting.Thin French beans: three minutes. Standard green beans: four to five. Runner beans, sliced: four or five. You want bright green with a definite squeak against the teeth and no raw taste.
5. Refresh in iced water immediately.A bowl of cold water with ice in it, ready before you start. Beans carry a lot of residual heat and will keep cooking in the colander. Thirty seconds in the ice bath stops it dead and sets the colour.
6. Drain thoroughly and hold.Once cold, drain and pat dry. They will sit in the fridge for a day, which makes them one of the easiest things to prepare ahead for a big meal.
7. Reheat in fat, not water, at the last moment.A minute in a pan with butter or olive oil, garlic if you like, salt and pepper. Or thirty seconds back in boiling water and straight into butter. They should be hot, not cooked further.

Tips

• Runner beans need stringing along both edges unless they are very young, and slicing on a diagonal. A runner bean slicer is a single-purpose gadget that is genuinely good at its job.
• Frozen green beans are already blanched. Cook them from frozen in boiling water for two or three minutes, or straight into a hot pan.
• Toasted flaked almonds, brown butter, lemon zest, anchovy, shallot and a mustardy vinaigrette all work with beans and all are added after cooking.
• Beans in a salad want the same treatment — blanched, refreshed, dried and dressed at the last minute so the acid does not dull the colour.

Common mistakes

• Steaming a large quantity of beans — Steam is slower than boiling water and the beans in the middle spend too long getting there, so they go drab.
• Skipping the ice bath and draining into a colander — A hot pile of beans keeps cooking for several minutes on its own heat.
• Dressing them with vinaigrette while hot — The acid strips the colour within minutes. Dress at the table.

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