McDonald's burger with two all-beef patties and special sauce is the Big Mac.
The Big Mac is built with two beef patties, shredded lettuce, cheese, pickles, minced onions, and a three-part sesame-seed bun. The extra middle section of the bun separates the patties and gives the sandwich its distinctive stacked appearance. Its “special sauce” is commonly described as similar to Thousand Island dressing, although the exact commercial recipe has changed over time.
A McDonald's franchisee in the Pittsburgh area created the sandwich in 1967. It expanded nationwide in 1968 and became one of the chain's signature products. The famous ingredient jingle—“Two all-beef patties, special sauce, lettuce, cheese, pickles, onions, on a sesame-seed bun”—was commissioned in 1974 and helped make the recipe memorable.
The Big Mac is sometimes confused with the Whopper, Burger King's flagship burger, or the Quarter Pounder, which uses a single larger beef patty. Its name has also entered economics through The Economist's Big Mac Index, which compares currencies using the price of the widely sold burger.