Rocky Mountain oysters
Rocky Mountain oysters, also known as prairie oysters, are a North American culinary name for edible offal, specifically buffalo or bull testicles. They are usually peeled, coated in flour, pepper and salt, sometimes pounded flat, then deep-fried. This delicacy is most often served as a starter.
It is a well-known novelty dish in parts of the American West and the Canadian Prairies where cattle ranching is prevalent and castration of young animals is common ("prairie oysters" is the preferred name in Canada, where they may be served in a demi-glace, not deep-fried). In Oklahoma and North Texas, they are sometimes called calf fries but only if taken from very young bulls. In Spain and many parts of Mexico they are referred to as "criadillas" and are colloquially referred to as huevos del toro (literally, "bull’s eggs" but huevos is also a Spanish slang term for testicles) in Central and South America. Rocky Mountain oysters are sometimes confused with lamb fries or animelles (lamb testicles), which are served in a manner similar to Rocky Mountain oysters. A few other descriptive terms, such as "cowboy caviar," "Montana tendergroins," or "swinging beef," may be used.
The dish, purportedly cowboy fare, is most commonly found served at festivals, such as the ones in Montana and Phoenix, Arizona, amongst ranching families, or at certain speciality eating establishments and bars. Eagle, Idaho, claims to have the "World's Largest Rocky Mountain Oyster Feed" during its Eagle Fun Days (typically the first weekend in June).