Tom kha kai is a soup built on the balance of galangal, lemongrass, and kaffir lime — aromatics that are unforgiving to overextraction. DeeDee Niyomkul, who runs Nan Thai Buckhead in Atlanta after transforming the former Chai Yo Modern Thai, understands these aromatics the way you only can if you've been cooking with them your whole career: not as flavors to add, but as a ceiling not to exceed.
She simmered her galangal and lemongrass in coconut milk at 165°F — below a boil — for fifteen minutes, then removed them before they crossed into bitterness. Mushrooms went in at the ten-minute mark rather than the beginning, retaining their texture. Fish sauce came off-heat, not in the boil, because heat volatilizes the fermented complexity. The finish was fresh lime juice, not bottled, added at the last thirty seconds.
Nan Thai Buckhead is the room DeeDee Niyomkul built for this kind of cooking. Bobby's tom kha, per judges, over-extracted the aromatics. There are fifteen minutes between delicate and bitter, and she spent them perfectly.