The rivers of France abound with various kinds of small trout, and one of the most popular ways of cooking them is “au bleu”—the boiling vinegar in which they are plunged turning them a vivid blue. But to obtain a perfect dish of “truites au bleu”, it is essential that the fish should be perfectly fresh, rapidly cleaned as soon as it is caught, and at once immersed in the boiling vinegar, without being either scaled or washed. Many a country inn throughout France is noted for this dish, and within three or four minutes of being removed from the cool water of a stream or brooklet, the trout find themselves in the boiling, aromatic and highly seasoned courtbouillon.
For this, equal parts of water and vinegar are used, onions,
They can also be served cold, with a mayonnaise sauce.