This section is from the book "Soyer's Standard Cookery", by Nicolas Soyer. Also available from Amazon: Soyer's Standard Cookery.
Take a nice trout from half a pound to two pounds in weight. Clean and trim well. Then cut on each side about eight or ten incisions. Season well with salt and pepper, according to taste. Take two ounces of butter, half a teaspoonful of anchovy paste or sauce. Rub half a shallot on a cold plate and throw the shallot away. Mix a teaspoonful of flour with the butter on the plate you have rubbed with shallot. Add a large teaspoonful of capers (if at hand). Place your trout in a well-buttered paper-bag with all the ingredients. Have ready half a cucumber blanched in boiling water for six minutes and cut up in small dice. Also two medium-sized carrots cooked in boiling water, salt, and a little sugar, cut small. Slice two large gherkins and twelve small new cooked potatoes. Place all the above around the raw fish in the paper-bag, adding the juice of one lemon. Put one tablespoonful of melted butter over the vegetables, etc. Seal bag and place carefully on grid. Allow for one trout, half a pound, twenty minutes; one pound twenty-five minutes; one and a half pounds, thirty-five minutes; two pounds forty minutes - in hot oven (350 Fahr.).
Any fish can be cooked in the same way by shortening or adding to the garnishing of the above recipe. Fresh mushrooms are always very welcome in cooking trout, salmon, tur-bot, whiting, halibut, eels, or any other kind of fish. This is a matter to be left to the taste of the cook. But never omit to mix up the flour with the cold fresh butter, to be laid well on the top of the fish. If you desire a sauce, put half a glass of claret with your fish in the paper bag.
 
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