This highly traditional recipe, which is given in the Faroese cookery book by Oluva Skaale and Marius Johannesen (Matur og matgerð, 1974), was expounded to me as follows by Jon Olavur Joensen of Holte in the Faroes. He explained that fresh young cod are the best fish to use; but that whiting are also good and that a mixture of cod and haddock is satisfactory. The mutton fat to be used is garnatálg, to be taken from around the sheep’s kidney.