Take the tails of two dozen boiled crayfish, and cut them up into dice. Remove the meat from the claws, chop it up with the trimmings of the tails, and an equal quantity of fresh mushrooms; put them into a basin, and add ten eggs, a little salt and nutmeg to season, and a small pinch of finely-chopped parsley; whip them well for three minutes. Warm four ounces of butter in an omelet-pan, add the eggs, etc.; let it thicken a trifle, and then put the tails - previously mixed with one tablespoonful of white sauce reduced with a little meat-glaze - in the center. When cooked remove the omelet, roll it up, put it into an oblong dish, and serve.