The best fish stock I have ever made or used came from the bones, head and trimmings of a magnificent turbot which, for a very special occasion, I had ordered to be delivered express from the quayside in Cornwall. We had turbot sashimi for dinner, and the stock played its part in some very delicious cooked fish dishes thereafter. Of course, you don’t have to have fresh turbot; bones and trimmings from all sorts of white fish – plaice, lemon sole, Dover sole – make excellent stock, as do salmon heads and bones. To make it better still, put in, if you can, a little of the flesh as well, or perhaps a small plaice or a bit of a different fish altogether, such as cod or haddock.