Heat 50 g (2 oz) of butter in a pan. Add 100 g (3½ oz) of carrots, 80 g (3 oz) of onion and 20 g (⅔ oz) parsley stalks, all cut in fine Mirepoix; 1 small sprig of thyme and ½ a bayleaf. Cook together till lightly browned. Add 1 kg (2¼ lb) salmon head and a pinch of coarsely ground pepper; cover with a lid and allow to stew for 15 minutes.
Drain off the butter, add 1 litre (1¾ pt or 4½ U.S. cups) of red wine and reduce by half. Add 5 dl (18 fl oz or 2¼ U.S. cups) fish Espagnole and allow to simmer gently for 1 hour. Pass firmly through a strainer into a clean pan.
Allow to rest for a few minutes and then carefully remove any fat which has risen to the surface of the sauce.
Add an extra 5 dl (18 fl oz or 2¼ U.S. cups) of red wine and the same amount of Fish Stock; simmer gently with careful skimming and reduce to the required consistency. Pass the sauce through a fine strainer and finish with 1 tbs of anchovy essence and 150 g (5 oz) of butter, mixed in well.
This sauce is specially suitable for serving with salmon and trout.