The burger is called the "Top Chef Grand McExtrem" and is a variation of their Grand McExtrem burger. The "Extrem" isn't for "extreme" but for "Extremaduran," a region of Spain, whose cuisine is known for "its simplicity, its lack of clutter and its low cost," according to Wikipedia.
Between two halves of a sesame seed bun, you'll find two beef patties, a sofrito featuring mushrooms, asparagus, tomatoes, and onions, crunchy roasted corn, a creamy sauce made with soy and mayo, and Batavia lettuce.
Among some of the more interesting toppings some of the other Top Chef contestants tried were fig compote, honey, mustard greens, Brie, and caramelized kumquats. What could have been, right?