You will need the skins of the boiled potatoes that you put aside. Be careful: you need them cold and dry.

Heat the oil in a pan. We're going to shallow fry them. When the oil is hot - make a test with a potato skin - fry the skins in two or three batches, so as not to overcrowd the pan. Turn them with a ladle or with frying tongs, and cook them until they are golden and crisp.

When the potato skins are well browned and crunchy, lift them with a slotted spoon and lay them in a dish lined with a sheet of cooking paper to absorb the excess oil.

Sprinkle with salt - better a flake salt, such as Maldon salt or fleur de sel - and eat them immediately, until they are crisp.