When you slow-cook cultivated white mushrooms in a closed clay pot, such as a Chinese sandpot, an extraordinary alchemy takes place. These ordinary mushrooms, which normally taste quite bland, acquire an earthy flavor, almost as deep as that of wild ones.
I never cease to be amazed at the transformation, which I attribute to the clay vessel. My theory, stated earlier in this book, is that wonderful flavor can often be developed when there is no interference between earth—that is, the clay—and food. I think this simple recipe proves my point.