Foie gras
Foie gras (French for "fat liver") is the liver of a duck or goose that is swollen by overfeeding.
Along with truffles, foie gras is considered one of the greatest delicacies in the world of French cuisine. It is very rich and buttery, with a delicate flavor unlike regular duck or goose liver. The geese or ducks used in foie gras production have their throats held open temporarily to allow the farmer to pour feed directly into the stomach. The excess feed, usually corn, causes large amounts of fat to deposit in the liver, producing the buttery consistency. Some people regard this forced feeding (known as 'gavage' in French) as cruel.
Foie gras is sold fresh, frozen, partially cooked, and fully cooked. It can be whole, "en bloc," "en terrine," or made into pâté.