This fascinating sandwich is found in some areas in the US, particularly in the Ohio River Valley, made from sliced pig or calves brain, which is heavily battered and then deep-fried. Immigrants from Holland and Germany who were keen on eliminating any type of waste started this sandwich. However, the earliest versions were typically served with fried potatoes and onion rings, while the modern version usually consists of fried calves brain stuffed in sliced bread or buns. Although, most of the flavor in the sandwich comes from the batter, as the brains only have a mild taste and a custardy texture.