To make your quick fish sauce:
Place the clam juice, water, wine, onions, parsley and mushrooms in a 6-cup saucepan and simmer for about 30 minutes. The liquid should reduce to about 2 cups.
Strain the stock and taste, add seasoning as necessary. This stock tends to be salty from the clam juice so you may need to adjust the salt in your recipe.
If you don't use the fish stock right away you can place in a tightly sealed jar or other contain and refrigerate up to a week. If you need to store the leftover stock for a longer period then you can put the stock in a freezer storage container and freeze for up to 6 months