This is an unusual soup, using several ingredients that are found only in Southeast Asian cuisine. The broth is light enough to mesh with the delicate musty flavor of the Helvella lacunosa. You may have to go to an Asian market to find some of the ingredients here. The bean thread noodles are quite common, and often go by the name of saifun. They become clear and slightly rubbery when cooked. Galangal, a spicy root that appears in Thai curries, resembles ginger in some ways, although more bitter and not as spicy. You can purchase it in dried slices, which is what I used here. Shrimp paste is common throughout Southeast Asia, made with crushed fermented shrimp, salt and spices. It smells very strong, but provides an essential bit of complexity when used in moderation. Although the combination of chicken broth and shrimp paste might seem a little odd, I find that the tiny amount of shrimp paste used here - in combination with the galangal - gives the broth an added depth which meshes nicely with the helvella. You may also substitute vegetable or fish stock with good results.
Sauté in the bottom of a large soup pot for a few minutes, until the shallots and leeks get soft. Add:
Simmer, covered, for 1/2 hour. While the broth is simmering, begin heating another large pot of water (about 4 qts.) and bring to a boil. About 15 minutes before you wish to serve the soup, immerse in the boiling water:
Turn the burner off, and let the noodles soak for 15 minutes. While the noodles are soaking, prepare:
Put the tofu cubes and brocoli flowerettes into the simmering mushroom soup broth, stir and cover again. Let simmer for about 5 more minutes, and season with additional salt and white pepper if desired. Be sure not to let the brocoli get soggy. The soup should be served as soon as the brocoli is barely cooked.
When you are ready to serve the soup, strain the bean threads and place about a cup of bean threads in the bottom of each bowl. Ladle or pour the soup broth into each bowl of noodles, distributing the tofu and brocoli on top. You might chose to remove the piece of galangal from the broth at this time, since it makes for a strong flavored surprise when you bite into it. Immediately before serving, sprinkle on top of each bowl of soup: