Put the potatoes into a wide, shallow pan in which they fit in a single layer. Add 2 tablespoons salt and 1 quart cold water (just enough to cover), bring to a boil, and leave to boil rapidly until the water has evaporated. Then turn the heat to low and continue to cook for a few minutes, gently turning the potatoes over occasionally, until they are dry and the skins are wrinkled and covered in a thin crust of salt.