====== Fish Stock ======

===== Ingredients =====

  * 2 pounds bones and heads of lean, white-fleshed fish, such as snapper or bass, gills removed
  * 1 teapoon kosher salt
  * 2 tablespoons vegetable oil
  * 1 cup diced yellow onion (about 1/2 large onion)
  * 1 cup diced fennel bulb (about 1/2 large bulb)
  * 1 medium leek, minced
  * 2/3 cup diced celery (about 2 large ribs)
  * 1 cup dry white wine
  * 4 cups water
  * 2 sprigs flat-leaf parsley
  * 2 sprigs tarragon
  * 1 bay leaf
  * 5 whole black peppercorns

===== Directions =====

  - Place fish bones and heads in a large bowl and cover with cold water. Stir in kosher salt until dissolved. Let stand 1 hour. Drain, then rinse fish under cold running water, washing away any large areas of blood, such as near spine.
  - In a large saucepan, heat oil over medium-high heat until shimmering. Add onion, fennel, leek, celery, and garlic, and cook, stirring, until vegetables have softened slightly, about 3 minutes. 
  - Stir in fish heads and bones.
  - Add wine and cook, stirring, until it begins to steam.
  - Add 4 cups water (liquid should just barely cover heads and bones; if not, add just enough more to barely cover). Add parsley, tarragon, bay leaf, and peppercorns.
  - Bring liquid to a bare simmer, then lower heat so that it stays just below a simmer, with only the occasional bubble.
  - Cook for 20 minutes. Using a spoon, skim off any scum that accumulates on the surface.
  - Strain fish stock through a fine-mesh strainer, then chill. 

Fish stock can be kept refrigerated, covered, for up to 5 days or frozen for up to 3 months.