Nightfin Soup

Nightfin Soup is an exceptional bit of food for healers. Nightfin Soup is generally most valuable during long boss encounters that are mana intensive. Combined with other items such as a Mageblood Potion and Brilliant Mana Oil, a caster even in mediocre gear can have very good mana regeneration. The soup is cooked by those with a skill level of 250. This requires a Cooking Fire. The components are:
 * 1 Raw Nightfin Snapper
 * 1 Refreshing Spring Water

Source
Nightfin Soup can now be learned from Cooking Trainers. Before the Cataclysm, Recipe: Nightfin Soup could be purchased from in Steamwheedle Port in Tanaris