Here is my my g-g-grandmother's recipe which I have translated and added some modernized text.
Donald E. Asp
It smells good, it tastes good, and it brings to mind wonderful Swedish Christmas traditions that we still keep. The dish is not based on salt and has nothing to do with anchovies and you DO NOT USE caustic soda. But is exactly what the name of the dish says…Lut = lye fisk =fish. It is a very strange dish to prepare if it is done from scratch and is usually prepared now from a frozen variety. As in all unusual
dishes often the establishment selling it does not know if the product has gone bad, and I have experienced spoiled lutfisk… not fun. But if prepared properly it is delicious. For those of you with a desire to know how to make it.
Take two lbs. of stockfish (dried fish, preferably cod, lincod or saithe caught in early summer) and cut each fish in three pieces. Place the pieces in a wooden tub and soak them for a week in water (which should be changed daily). Remove the pieces, clean the tub, and cover the bottom with 1/4 lb. of slaked lime. Prepare a lye from 1/3 lb. of washing-soda (WARNING do not utilize caustic soda or natriumhydroxide) (2 lbs. of
birch ashes will also do) add enough water to cover the pieces, and pour the lye over the fish pieces. As they swell, add more water to keep them covered. When the pieces are soft enough to allow a finger to penetrate easily (after about a week), remove and rinse them, clean the tub, replace the pieces and soak them in clear water for another two weeks. During the first week the water should be replaced daily. Cook in boiling salted water at simmering temperature for about 20 minutes. Drain well and serve with a white sauce with freshly ground pepper and sea salt. Allow 1/3 lb per serving.