Mussel and Shiitake Mushroom Dashi

This is one of many examples of how a simple Japanese dashi can be used as the base for an elegant—and fat-free—first-course soup. The mussels are steamed in a small amount of the dashi, the top shell is removed, and the mussels are served in the dashi with shiitake mushrooms and fine vegetable julienne. You can serve the soup in wide bowls, but I prefer Japanese-style black lacquer bowls with lids.

The dashi can be prepared a day or two in advance, and t