The Impossible Slider normally comes topped with smoked cheddar cheese. The new vegan alternative is made by GoodPlanet Foods, and White Castle hopes to expand the offering in the future.
In addition to the Impossible Slider, White Castle offers a number of plant-based sliders in both their restaurants as well as the frozen food aisle of grocery stores. There's the Veggie Slider (made with a Dr. Praeger's vegan patty), which is available in both White Castle restaurants and in grocery stores as well as the Black Bean Slider, which can only be found at grocery stores.
Photo via White Castle.