Some of fast food’s splashiest plant-based chicken rollouts have seriously impressed us in the past. First, there was the debut of Impossible Chicken Nuggets in 2021, a product that managed to capture the brothy flavor of real cooked poultry and deliver both crunch and chew without tasting springy or spongy. (Burger King tested these nuggets at various locations last fall.) Then, KFC released Beyond Fried Chicken in January 2022; these were essentially nuggets as well, and tasted “pretty spectacular,” according to our taste test. Both of these, however, were small-format chick’n products. The Impossible Original Chick’n Sandwich at Burger King...