A patty melt is a type of hamburger consisting of a hamburger patty and Cheddar or Swiss cheese between two slices of bread (traditionally rye, though sourdough is sometimes substituted). Patty melts are sometimes prepared using marbled rye bread. In some places, especially in the U.S., a patty melt can consist of only the patty of a hamburger, with cheese, on a single piece of toast/bun. The hamburger is then fried with butter on a frying pan so that the cheese melts thoroughly. The first patty melts were served in Kara's Diner in Philadelphia. The hamburger patty was cooked on a griddle, then smothered with onions and Swiss cheese, they are served on toasted rye bread with plenty of Russian dressing. They embellish on the traditional cheeseburger, and further take the burger back to its roots by being served on bread versus a bun.