Every November, celery performs countless tasks: It perfumes the holiday turkey, lending moisture from the inside out; it’s the backbone of the stock in gravy; it adds bite and vegetal flavor to stuffing. But rarely does this tireless Thanksgiving staple get any thanks. “It’s hard to make it the center of the spectacle, but on the back end, it’s everywhere,” said Ignacio Mattos, chef and owner of Estela, Flora Bar and Café Altro Paradiso in New York City.