In the world of broccoli, florets usually have all the fun. That is, until our Test Kitchen figured out a way to use the cruciferous vegetable's leftover stems: as a base for cannellini-broccoli soup. After a quick sauté with leeks, the stems are simmered with chicken broth, beans and a Parmigiano-Reggiano cheese rind, then puréed until light and creamy. It's a clever way to turn an oft-overlooked piece of produce into something unusually tasty.