Which restaurant chain's signature product is the Whopper?
The restaurant chain whose signature product is the Whopper is Burger King. The Whopper is a flagship hamburger offered by Burger King and is one of their most well-known menu items. It consists of a flame-grilled beef patty, sesame seed bun, lettuce, tomato, pickles, onions, mayonnaise, and ketchup. The Whopper has become an iconic fast food burger and has been a staple on Burger King's menu for many years.