It almost seems too simple to ask the question, How do you boil potatoes? But that’s because the real question is How do you avoid mushiness on the one hand or gumminess, on the other?
One large boiled potato in salted water
Well, the answer is in cooking your potatoes in large chunks. I generally cook Idaho or russets, since I prefer them for mashed potato. And if I don’t want a mash, but roasted chips (wedges) or a baked potato instead, these varieties are ideal. I first scrub the taters with a stiff veggie brush under a running tap. I then cut each potato in half, and then cut that down the middle again — so it ends up in quarters. Leaving the skin on, I put them all in a medium or large saucepan, depending on whether I’m cooking one or two. I add salt, about a teaspoon, and cover with water. Bringing the water to a rolling boil, I put a lid slightly askew on top, and reduce the heat to a medium-high setting (usually 7 on my induction hob). I set the timer for a minimum of 13 minutes, though 15 is usually not too much. When they are confirmed done with a knife poked into the middle of a chunk, I drained them and allow them to cool. The skin can then be peeled off quite easily (and I feed the skins to my dog!). They will already be peeling at the edges, usually, especially if they’re rather thick.
Potatoes cooked this way are perfect for mashing: neither gummy nor too soft. Regarding cooking time, my advice is err on the side of longer and softer rather than shorter (and harder). As long as you drain the potatoes more or less immediately, they won’t end up watery. But it’s not pleasant when you begin mashing only to find that you have some not-quite-done hard chunks in the mix. If you do find that, the best remedy is to take those pieces out and microwave them briefly until they match the softness of the rest. And another tip: even though you will have washed and scrubbed the potatoes before they went in, it’s a good idea to swish a bit of water and a paper towel around the pot, just to remove any grit or residue before replacing the cooked potatoes in the pot and doing the mash.