Food & Wine's Kay Chun sneaks a small piece of creamy, nutty Parmesan cheese into this lovely soup, giving it an excellent flavor boost. To make it even more special, she serves the silky bisque topped with a nutty, crunchy and vibrant walnut-and-parsley gremolata. The celery root and leeks give this creamy soup a lightly earthy flavor, and the freshness of the herb gremolata really brightens it up. This soup is a wonderful make-ahead option, since it can be refrigerated for two days. Swap vegetable stock for chicken stock for a hearty meatless Monday dinner.