As an alternative to crayfish sauce, try making crayfish butter, which is mainly used to enrichen sauces. By incorporating it in a cream sauce, it will improve both the flavour and depth of the sauce – lobster butter is also made in the same way. Only the shells are needed and it can be made from shells left over from another recipe. If using fresh crayfish, save the tail meat either as an accompaniment to the dish incorporating the butter, or possibly use it in a salad. The keeping quality of the butter is very good – 1-2 weeks in the refrigerator, or even longer in the freezer. Make a roll of it using greaseproof paper and cut off as much as you need while still frozen – it will keep for many weeks. I find it is better to chop up the shells a little before putting them in the blender, as the machine will accept them better this way.