Burger King a bunch of beef-loving customers into eating a vegetarian version of the Whopper — using the alternative beef Impossible Burger. BK also announced the Impossible Whopper would be available at 59 Burger King restaurants in the St. Louis area, where they’ll be testing the concept. It’s primarily made of water, soy protein, coconut oil, sunflower oil, and leghemoglobin — the source of the meaty flavor. For those not in the St. Louis area, Impossible Burger can also be found at select Applebee’s, Red Robin & White Castle locations