In potentially the biggest coup so far for meatless burgers, Burger King has announced plans to test-market a meatless version of the Whopper, furnished by Impossible Foods. Burger King joins White Castle in selling the meatless burgers or analogue meat. 

The Impossible Whopper is due to be rolled out this week at Burger King outlets in St. Louis. If the test goes well, the meatless burger will be sold at Burger Kings nationwide. The Impossible Whopper will be sold in a branded wrapper and will cost about a dollar more than a regular Whopper.

Burger King says that Impossible’s resemblance to ground beef, based on a proprietary process to cultivate a protein that incorporates much of the real thing’s taste, is largely responsible for the chain’s decision to go ahead with the test market.

“People on my team who know the Whopper inside and out, they try it and they struggle to differentiate which one is which,” chief marketing officer Fernando Machado told the New York Times.

Impossible products have been sold at White Castle restaurants nationwide since December, and Red Robin restaurants started carrying them this week. But with 7,200 locations, Burger King could be the biggest foodservice outlet for Impossible Foods.