KFC created the Double Down sandwich, which uses two fried chicken fillets instead of conventional bread buns.
KFC introduced the Double Down in the United States in 2010. The original version placed bacon, cheese and sauce between the two chicken fillets, making the fried chicken itself the outer structure of the sandwich.
The product attracted attention because it reversed the usual sandwich design. Rather than placing a chicken patty between bread, it used chicken as both the top and bottom layers.
The Double Down has appeared in multiple country-specific versions, and ingredients have varied over time. Those variations do not change the defining idea: fried chicken fillets replace the bun.