Big Mac sauce

The Big Mac is a brand of hamburger sold by the international fast food restaurant chain McDonald's. It was introduced by a Greater Pittsburgh area franchisee in 1967 and expanded nationwide in 1968, and is widely regarded as the company's flagship product. The hamburger features a three-slice sesame-seed bun containing two beef patties, one slice of cheese, shredded lettuce, pickles, minced onions, and a Thousand Island-type dressing advertised as "special sauce." Seasonal and regional variants have been offered, including chicken versions.

Source: Wikipedia