|Lutefisk (on the upper left side of the plate) as served in a Norwegian restaurant, with potatoes, mashed peas, and bacon.|
The origin of lutefisk is unknown. Legends include the accidental dropping of fish into a lye bucket or sodden wood ash containing lye under a drying rack. Another claims the practice enabled storing fish outdoors. Cold temperature acted as a preservative and the lye deterred wild animals from eating the fish
Lutefisk is made from dried whitefish (normally cod in Norway, but ling is also used) prepared with lye in a sequence of particular treatments. The watering steps of these treatments differ slightly for salted/dried whitefish because of its high salt content.
The first treatment is to soak the stockfish in cold water for five to six days, with the water changed daily. The saturated stockfish is then soaked in an unchanged solution of cold water and lye for an additional two days. The fish swells during this soaking, and its protein content decreases by more than 50 percent, producing its famous jelly-like consistency. When this treatment is finished, the fish, saturated with lye, has a pH value of 11–12 and is therefore caustic. To make the fish edible, a final treatment of yet another four to six days of soaking in cold water, also changed daily, is needed. Eventually, the lutefisk is ready to be cooked.
After the preparation, the lutefisk is saturated with water and must therefore be cooked carefully so that it does not fall into pieces.
If one likes to have the lutefisk more firm in its consistence, one can spread a layer of salt over the fish half an hour before it is cooked. This will "release" some of the water in the fish meat. The salt must be rinsed off before cooking.
There are several ways to cook lutefisk:
Lutefisk does not need additional water for the cooking; it is sufficient to place it in a pan, salt it, seal the lid tightly, and let it steam cook under a very low heat for 20–25 minutes. An alternative is to wrap in aluminium foil and bake at 225 °C (435 °F) for 40–50 minutes.
Another option is to parboil lutefisk; wrap the lutefisk in cheesecloth and gently boil until tender. This usually takes a very short time, so care must be taken to watch the fish and remove it before it falls apart. Prepare a white sauce to serve over the lutefisk.
Lutefisk can also be boiled directly in a pan of water. Fill the pan 2/3 full with water, add 2 ts of salt per liter water, and bring the water to a boil. Add lutefisk pices to the water until they all are covered with water, and let it simmer for 7 to 8 minutes. Carefully lift the lutefisk out of the water and serve.
Lutefisk sold in North America may also be cooked in a microwave oven. The average cooking time is 8–10 minutes per whole fish (a package of two fish sides) at high power in a covered glass cooking dish, preferably made of heat resistant glass. The cooking time will vary, depending upon the power of the microwave oven.
When cooking and eating lutefisk, it is important to clean the lutefisk and its residue off pans, plates, and utensils immediately. Lutefisk left overnight becomes nearly impossible to remove. Sterling silver should never be used in the cooking, serving or eating of lutefisk, which will permanently ruin silver. Stainless steel utensils are recommended instead.