How to Make It
In a large saucepan, combine the stock with the lemongrass, ginger, chiles and lime zest and bring to a boil. Simmer over moderately low heat for 10 minutes. Strain and return to the saucepan. Discard the solids.
Add the cauliflower, shiitake and coconut milk to the stock and bring to a boil, then simmer over moderate heat until the cauliflower is crisp-tender, about 5 minutes. Add the chicken and edamame and simmer just until heated through, about 2 minutes. Stir in the lime juice and fish sauce and season with salt. Garnish with the cilantro and serve.