In Key Ingredient Rob Levitt (Mado, the Butcher & Larder) tackles abalone—which took him three purveyors to find—pairing it with bone marrow in a bruschetta that also features chiles, radish, fennel, and parsley. “You get a little hot, a little cold, a little land, a little sea, animal, vegetable—we can put the shell on for some mineral,” he joked. Next up is Jason Vincent of Nightwood, working with duck tongues.