===== Ingredients =====
  * 6 oz Parmesan rinds
  * 1 onion
  * 1 leek (white and light green parts)
  * ½ fennel bulb
  * 2 celery ribs
  * 1 bay leaf
  * 2 quarts water

===== Method =====

  - Rinse the rinds to remove any dust or waxy coating.
  - Combine everything in a pot.
  - Bring just to a simmer.
  - Simmer gently for 2–3 hours.
  - Strain through a fine mesh sieve.
  - Chill and refrigerate up to 5 days or freeze.