Galangal—a root similar to ginger, kaffir lime leaves, lemongrass, and fish sauce give this soup authentic flavor. Substitute ginger if you can't find galangal, and use 3 (2-inch) lime rind strips in place of the leaves. Reserve the shrimp shells; you'll need them to make the broth. Serve with rice noodles, if desired.
View Recipe: Tom Yum Goong