This simple soup is warming, light, and makes tasty use of those white daikon radishes that are so ample in colder months. I've always enjoyed daikon simply peeled and thinly sliced, but here its sharp flavor is mellowed and crisp texture is softened in the most lovely way. Any dried mushrooms work here. Wood ear mushrooms or shiitake mushrooms are classic choices, but porcini or morels are lovely too. It's all about adding some color, earthy flavor, and texture.