Tom Yum Base (Lemongrass, Galangal, Kaffir Lime)
What it is
The hot-and-sour Thai aromatic broth base — fragrant, fiery, citrusy, and clear (in the nam sai version). Not a long-simmered stock but a fast, bright infusion built on a trio of fresh aromatics.
How it's made
A light stock or water is infused with bruised lemongrass, sliced galangal (not ginger — galangal is sharper, piney, medicinal), and torn kaffir lime leaves, plus Thai chilies and often shallots. Fish sauce supplies salt and umami; fresh lime juice supplies the sourness, added at the end so it stays bright; chili and sometimes a chili paste (nam prik pao, roasted chili jam) supply heat and color. It comes together in minutes — the aromatics are infused, not boiled to death.
Flavor profile
Explosively aromatic, hot, sour, salty, and savory all at once, with the unmistakable triad of grassy-citrus lemongrass, piney galangal, and floral kaffir lime. Bright and bracing; intensity is high but clean.
Culinary uses
The base for tom yum goong (shrimp) and its many cousins, and a template for hot-and-sour Thai soups generally. Often enriched with mushrooms and tomato. Without it — specifically without the aromatic trio: the soup loses its identity entirely. Substitute ginger for galangal or skip the kaffir lime and you get a generic sour soup; the precise aromatics are non-negotiable and define the dish.
Regional variations
Tom yum nam sai (clear) vs. tom yum nam khon (creamy, enriched with evaporated milk or coconut milk and chili jam). Central Thai versions differ from those of the south and northeast; the creamy version is more common abroad.
Cultural & historical context
Tom yum is one of Thailand's most internationally recognized dishes and a showcase of the Thai flavor philosophy: simultaneous balance of hot, sour, salty, sweet, and umami in a single spoonful. Its aromatics are also valued in Thai traditional medicine.
Reference notes
Tags: `broth`, `aromatic`, `hot-and-sour`, `lemongrass`, `galangal`, `kaffir-lime`, `umami-base`, `thai`. Related ingredients: lemongrass, galangal, kaffir lime leaf, Thai chili, fish sauce, nam prik pao. Related cuisines: Thai. Suggested links: Galangal, Lemongrass, Kaffir Lime, Tom Kha Base, Fish Sauce. The galangal-vs-ginger distinction is a perfect "teach something they don't know" note.