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Brook Trout Au Bleu
Procure three medium, live brook trout and keep in a basin with plenty fresh water. Have in a saucepan one sliced carrot, one sliced onion, two cloves, one bay leaf, two gills good vinegar and one gallon cold water. Season with one tablespoon salt and let boil for fifteen minutes. With the left hand take hold of a trout, by the head only, hold it down on a board and close the eyes with the fingers, then with the point of a knife in the right hand break the spinal bone at the end of the body near the tail. With the knife cut it open through the belly and remove the intestines, still holding the fish by the head and being careful never to touch the body of the fish with the fingers. Lay the trout on a plate, pour a good tablespoon of vinegar over, then proceed the same with the two others. Put the trout in boiling water and let boil for five minutes, remove the pan from the fire and let rest on a table for five minutes. Lift them up with a skimmer, dress on a hot dish with a folded napkin, decorate the dish with parsley and six quarters lemon and serve.
This is the classic truite au bleu, and everything about the handling exists to serve one end: the blue colour comes from the fish's own slime coat reacting with acid, so the skin must never be touched or rinsed.
- The hinge: do not touch the skinThe natural mucus on a just-killed trout turns slate blue when vinegar hits it. Handle the fish by the head only, never wipe or rinse the body, and pour the vinegar over immediately. A fish that has been wiped, iced for days, or scaled will poach white or grey rather than blue.
- GillsTwo gills is one cup of vinegar for the court bouillon, plus about a tablespoon poured over each trout just before poaching. The recipe specifies only 'good vinegar'; a plain white vinegar keeps the broth pale.
- Sourcing live troutFew markets keep live trout now. A trout dispatched at a farm gate or caught and cooked streamside within the hour is the practical route; anything longer and you are making poached trout, which is worth doing but will not go blue.
- The court bouillonOne gallon of water with carrot, onion, cloves, bay and vinegar, boiled fifteen minutes and salted with a tablespoon, is the whole flavour base. Boil it before the fish are killed so there is no delay between vinegar and pan.
- Poaching timingFive minutes at a boil plus five minutes off the heat, which suits the 'medium' trout the recipe calls for. The flesh should pull cleanly from the backbone; larger fish need a minute or two more, and a hard rolling boil will split the skin and lose the colour.
- ServingThe folded napkin on the platter absorbs the poaching liquid so the fish is not sitting in a puddle. Melted butter, or a hollandaise, is the usual accompaniment. The recipe lists the lemon quarters among the decoration, though they are equally there to be squeezed over.
- YieldThree trout, one per person, as a first course or a light main.
Au bleu is one of the oldest tests of freshness in European cookery: the trick only works on a fish killed at the pan, which is why the dish belongs to Alpine inns, trout ponds and fishing lodges rather than to city kitchens. It is generally traced to Switzerland and Savoy, where the cooking was as much proof as preparation. The vinegar poured over the fish at the last moment does double duty, setting the blue and firming the flesh so the skin stays whole in the water.