The ancestors of the frogs were the stegocephalia; dating back 360 million years, they were the first vertebrates to leave the water. The frog's life cycle always reproduces this transformation: it starts life as an embryo inside an egg, then it grows and becomes a tadpole, a tiny fish that develops little by little. When its gills turn into lungs, it must then leave the water in order to breathe.
Wherever they were found, frogs have been eaten since ancient times: their bones have been found in archeological digs in France, Switzerland, and Germany. During the Middle Ages, they were authorized as a food to be eaten in Lent, hence the nickname they were given by Grimod de la Reynière, Alouettes de Carême (Lenten larks).
According to Alexandre Dumas, frogs were given pride of place on tables in France, Italy, and Germany in the 16th century. In his L'Art de la Cuisine Française au 19e siècle: Traité des Entrées chaudes, Carême devoted several pages to the frog, offering a number of different recipes (Chapter 36). .
However, perhaps because of their kinship with toads, the English and Dutch still obstinately refuse to eat frogs. This was an annoyance to Escoffier while he was working in London. He secretly served them during a large party for 600 people held in honor of the Prince of Wales at the Savoy Hotel as his famous Cuisses de Nymphes à l'aurore (Thighs of the dawn nymphs), which has gone down in the annals of gastronomic history.
The French are not the only "frog-eaters", a name the English gave them in the 19th century, The Quebecois also love them.
The same occurs in the United States, in the states of Arkansas and Texas, but especially in Louisiana: there are a large number of recipes from French settlers, while the city of Rayne has even been known by the nickname of "Frog City" since the 1880s because of the chef Donat Puchau, who made frogs popular in many New Orleans restaurants.
Wild frogs are rare. They may be found locally in the Dombes and Burgundy regions of France.
Most come from farms in Europe (France, Hungary, Romania), the Middle East (Turkey, Egypt), Asia (China, Thailand, Taiwan), and in North America, especially in Quebec.
Frogs are often found whole and alive. But they are mostly found as fresh or frozen frog's legs. Frogs are either presented Lyon style (forelegs, trunk, and back legs), or Paris style (back legs only).
Frogs purchased live need to have their skin removed, before their backbone is split, while their legs are still attached. They should then be placed in very cold water for several hours to clean them of their viscous membrane. The water should be changed often. Once well dried, they are kept in a cool place.
Frozen frog's legs are thawed in milk for 30–45 minutes.
Frog's legs can be pan-fried with garlic, or battered and fried, as in tempura. They can be used in soup, served meunière-style, fricasseed, in blanquette, or au gratin with Mornay sauce. There are also a large number of French regional recipes.
Escoffier described his Cuisses de Nymphe à l'aurore as follows: the legs and thighs are "immersed in an court-bouillon aromatized with fragrant plants, then cooled and coated in a chaud-froid sauce with pink paprika". They were placed on a square plate decorated with tarragon leaves and everything was covered with a fine chicken aspic. The plates were served embedded in blocks of ice in order to keep the aspic cool.
Fresh frogs should be kept at 2–4ºC for up to 48 hours.
Frozen frogs should be kept in the freezer, without breaking the cold chain.
Frog meat is very lean and high in protein. They also contain a good deal of minerals and B vitamins.
Dozens of frog species exist worldwide.
The best-known varieties in Europe are the European green or edible frog; the pool frog,measuring 4–12 cm in length and weighing 100 g on average; the marsh frog, a little larger and also found in the Middle East and even China; and the Italian edible frog, which lives in the south of Italy.
Natives to North America are the bullfrog, which is much bigger (11–18 cm), and which has been introduced in other countries and is now considered an invasive species, and the northern leopard frog, which is small (6–8 cm). In Africa, the very large goliath frog, which grows to 30 cm, is eaten locally.
The European green frog has been decimated in France and other countries as a result of polluted watercourses, and is considered an endangered species. Capturing specimens of this species is banned or tightly controlled.