Ingredients (Makes about 1.5ltr/21/4pt)
Check the bones and trimmings contain no gill filaments or eyes. Wash thoroughly and place in a colander to drain.
Heat the oil in a heavy pan.
Add the vegetables, stir well then cover and leave over a low heat for 10 minutes. Add the wine and boil with the lid off for 1 minute.
Add the water and fish and bring to just below boiling, then skim well. Reduce the heat and simmer very gently, uncovered, for 20 minutes. Leave to cool.
Once cold, strain the liquid through a very fine sieve or, preferably, double muslin, discarding the debris.
Use immediately, or store covered and chilled in the fridge for up to 2 days, or frozen for up to 3 months.