How long to boil potatoes

Cold, and it matters more with potatoes than with almost anything else you boil. A potato dropped into boiling water cooks hard from the outside in, so the outer centimetre is already collapsing while the centre is still raw. Starting cold walks the whole potato up through the same temperatures together. Salt the water at the start rather than the end, because a potato only takes salt on while it is cooking.

Push a fork or a thin skewer into the thickest part. A done potato takes it with no resistance and slides back off when you lift. If it clings to the fork, or the point stops halfway, give it three more minutes and test again. Do not test with a knife: a blade cuts its own way in and will slide happily into a potato that is still hard in the middle.

Boil them skin on and peel afterwards if you want them peeled. The skin holds the potato together and keeps water out, so the result is drier and tastes more of potato. Peeled potatoes soak up water and run two or three minutes faster. To peel after, drop them into cold water for a few seconds and the skin comes away under your thumb.

Both mean the ordinary white potato, used where the everyday potato is something else. Irish potato is the widespread one, marking it out from sweet potato and from yam across much of West Africa, the Caribbean and the American South. English potato turns up the same way in some of those places. Either way it is the same vegetable and cooks identically, so go by size and cut, as above.