1 floury potato per person (e.g. Maris Piper, King Edward, Estima, Desiree)
About 20g coarse sea salt
1. Pre-heat your oven to 220C.
2. When the oven is up to temperature, wash the potatoes well, and prick each in a couple of places with a fork. Allow to dry slightly, while you tip your salt into a shallow bowl. Roll each potato in the salt to give an even coating, and then place on the middle shelf of the oven, preferably directly on the rack.
3. Cook for around an hour, then give them a squeeze – the potato should just give, and the skin should be distinctly crisp. If not, leave them for 10 minutes, and check again – if you overcook them, the insides will be dry, so it's important to be vigilant.
4. Take out of the oven and put whole on to plates: they shouldn't be opened until you're ready to eat, and then preferably by hitting them sharply so they burst, for maximum fluffiness. Do your thing with butter, and tuck in immediately.