au bleu a method of cooking certain freshwater fish, especially trout. The fish should be still alive when the procedure starts. It is then killed by banging its head on something solid, gutted through the gills, sprinkled with vinegar, and put at once into a boiling court bouillon. The effect of the vinegar on the mucus which covers the body of the fish is to turn it blue; and the sudden immersion in boiling liquid, given the totally fresh state of the fish, is to cause the body to arch into a crescent shape, a characteristic of this technique.
