PREPARATION:
- Rinse fish; cut out gills and discard.
- Trim tops and roots from onions, leaving most of the dried outer skin intact; cut into wedges.
- In stockpot or Dutch oven combine fish skeletons and heads, onions and celery. Add water, lemon, thyme, peppercorns and Herb Bouquet. Bring to a boil over high heat. Reduce heat to medium-low; simmer, uncovered, 30 minutes, skimming foam that rises to the surface.
- Remove stock from heat and cool slightly. Strain stock through large sieve or colander lined with several layers of damp cheesecloth, removing all bones, vegetables and seasonings; discard.
- Use immediately or refrigerate stock in tightly covered container up to 2 days or freeze stock in freezer containers for several months.
