In northern Scandinavia, the dry, cold conditions allowed fish to be preserved almost indefinitely by drying. The fish (mostly cod) was strung up and hung it from a rod or "stock" and allowed to dry. This produced "stockfish", called skreið ("sharp-fish") in Old Norse. During the Viking Age, the rock-hard skreið was prepared for eating by being beaten and pounded to break up the fibers, and served with butter. Skreið or stockfish became important in another legendary Scandinavian food, which is, however, not documentable until 1553, long after the close of the Viking Age: this is the (in)famous lutefisk, or "lye fish."
The earliest recipe for lutefisk comes from a 1553 German cookbook, Das Kochbuch von Sabina Welserin:
To prepare dried cod, from the gracious Lord of Lindau, who was Bishop in Constance. First take river water and ashes and add caustic lime [lye], which should be rather strong, and soak the dried cod therein. Allow it to soak for a day and a night, afterwards drain it off and pour on it again the previously described caustic lime solution. Let it soak again for a day and a night, put it afterwards in a pot and wash it off two or three times in water, so that the fish no longer tastes like lye. Put it then in a pot and put water therein and let it slowly simmer so that it does not boil over. Allow it to only simmer slowly, otherwise it becomes hard. Let it cook approximately one hour, after which, dress and salt it and pour salted butter over it and serve it. Also put good mustard on the outside in about three places. One must also beat dried cod well before it is soaked (trans. Valoise Armstrong 1998).
