Just as kale was transformed from an unappealing garnish to main menu item, chefs are looking for unlikely and usually tossed-out ingredients to become the next hot trend. Jonathan Wu, chef and partner at Fung Tu in New York City, saves broccoli stalks from the compost pile by slicing and serving them with beef and oyster sauce while Amanda Cohen of Dirt Candy uses beet, celery and carrot greens in stir-fries, pestos and pies.