sentences:  In their place, the chain is using a combination of chicken, vegetarian patties and mutton in place of beef.To promote continuing interest in the product, Burger King occasionally releases limited-time offerings ("LTO") on the Whopper such as the Windows 7 Whopper in Japan as a product tie-in with Microsoft's Windows 7 operating system.The hamburger contained seven stacked beef patties and measured high, weighed almost , and had more than .