Fish stock is also know as fish fumet. Make sure the fish bones you use are from lean fish and not fatty fish (avoid salmon or trout bones, for instance).
- Melt the butter in the bottom of a large stockpot. Add the mirepoix (onions, celery, parsnips, mushrooms), and place the bones on top. Cover the mixture with a piece of parchment paper cut to fit the pot. Sweat the mirepoix and bones over low heat for about 5 minutes, until the bones turn opaque and release some juices. Add the wine, bring to a simmer. Add the sachet (parsley, bay, peppercorns, clove and placed into a 4" square of cheesecloth and tied into a sack), and water to cover.
Bring to a simmer, skim any scum that forms, and continue to simmer for 45 minutes. Strain through a china cap layered with cheesecloth. Cool the stock immediately in an ice-water bath, transfer to a container and refrigerate. Skim off any fat that rises to the top.