British
Heat the oven to 200C.
Scrub the potatoes, dry them well and prick each one 4-5 times with a fork.
Rub the skins with the oil and half of the salt.
Bake directly on the oven rack for 60-75 minutes, until the skins are crisp and a knife slides easily into the center.
Cut a deep cross in the top of each potato and squeeze the sides so the flesh opens up.
Put 10 g of butter into each potato, season with the remaining salt and the pepper, scatter over the chives and serve at once.