Papas arrugadas is salt-encrusted boiled potatoes.
The dish is a specialty of the Canary Islands (the Spanish territory off the West African coast), but it is very similar to the salt potatoes made in New York State.
They are served as tapas in some restaurants, with red or green mojo sauces. You can eat them peeled or unpeeled.
Any variety of potato is used to make the dish, as long as it is small. New or salad potatoes work fine. In Tenerife, they often use the variety they call “papa bonita”, which stays small when fully grown.
The potatoes are washed and left unpeeled. They are put in a pot, with just enough water to cover them. A very generous amount of salt is added to the water (you can add too little, but not too much: as much salt as is going to adhere to the potatoes will adhere, and no more.) There should be enough salt in the water so that the potatoes will float. They are then boiled in this salted water until almost all the water has evaporated, leaving a salt crust on the potato skins. When the potatoes are cooked, you leave the stove burner on, and drain the water off the potatoes, leaving them in the pan. You then return the pot to the heat, and shake the pot to dry the potatoes. As they dry, the salt will become more visible on the skin.
Then turn off the heat, remove the pot from the burner, and cover the pot with a tea towel to let the potatoes steam dry, during which time the skin will wrinkle.
In the past, salt water would be used.
“Papas” means “potatoes”; “arrugadas” means “wrinkled”. “Papas” is a Canary Island word for potatoes; the actual Spanish word is “patatas”. “Arrugás” would be the Spanish word for “wrinkled”.