Lutefisk is dried cod that has been rehydrated by soaking in a strong alkaline lye solution (traditionally birch ash leached with water) for several days, producing a distinctive translucent, jelly-like texture before cooking. The technique is medieval - the Norse historian Snorri Sturluson described it in the thirteenth century - and originally evolved as a method of preparing the long-storage tørrfisk trade product back into something edible after months of sea or storage transport.
Modern lutefisk is a Christmas-season speciality served at a substantial fraction of Norwegian December dinners. The flavour is mild - the lye process leaches most of the cod's natural taste - and the appeal is largely textural and ceremonial. Lutefisk is divisive even within Norway: a serious portion of the population considers it a treasured tradition, and an equally serious portion considers it inedible and avoids it. The international cooking writer Jeffrey Steingarten famously wrote a long essay attempting and failing to make peace with lutefisk after a serious Norwegian Christmas trip.
The classic preparation is steamed or oven-baked lutefisk served with bacon, mushy peas, brown cheese sauce, boiled potatoes, mustard, and aquavit. The portion is large, the meal is long, and the social ceremony is essentially what gives lutefisk its cultural weight. Major Norwegian-American communities - particularly in Minnesota, the Dakotas and Wisconsin, where Norwegian immigration was historically substantial - have maintained the tradition with annual lutefisk dinners that some of the descendants attend more out of family duty than enthusiasm.
For the international visitor, lutefisk is the most difficult Norwegian traditional dish to recommend without context. We would rarely suggest it as a first introduction to Norwegian food. If you are in Norway during late November or December and curious to try the traditional dish on its own terms, the better Oslo restaurants with serious traditional menus - Engebret Café, Theatercaféen, Frognerseteren - serve credible lutefisk in season with the full classical accompaniments. Pair generously with aquavit and consider the whole experience cultural rather than purely culinary.