Dried shrimp gives this Chinese dish a punch of salty umami flavor. You can find it at an Asian grocery store in the frozen or refrigerated section. Look for small-sized dried shrimp, about a 1/4-inch in size. If you use medium or large dried shrimp, hydrate the shrimp with more water (1 cup for medium-sized shrimp, 1 1/4 cup for large) and for longer time (45 to 60 minutes), then chop it up into smaller 1/4-inch chunks. To make this recipe vegetarian, omit the dried shrimp and use four or five dried shiitake mushrooms, rehydrated, and sliced thin.