Tom Yum Goong

Prawn heads contain the tomally — the hepatopancreas — which is the most concentrated source of prawn flavour. The sautéing step before adding water creates a Maillard-flavoured base rather than a simple water extraction. Five minutes of sautéing builds flavour that an hour of simmering alone cannot replicate. The shells release chitin-bound proteins that contribute to the characteristic orange-pink colour of the stock.

The aromatic trio of Thai cooking — lemongrass, galangal, kaffir lime — are delivery systems for essential oils, not ingredients to be eaten. They are bruised before entering the pot to rupture the cell walls and release these oils into the stock. Five minutes of simmering is sufficient; longer begins to extract bitter tannins from the woody lemongrass base. These aromatics are moved aside before eating — they are fibrous and flavourless after their oils have been extracted.

Straw mushrooms hold their shape in liquid where button mushrooms would soften into mush. Cherry tomatoes are added at this stage — not with the aromatics — to preserve their structure and fresh acid contribution. They provide a different, brighter sourness than the lemongrass and kaffir lime, adding depth to the soup's acid profile.

Prawns provide a clear visual doneness signal: they curl into a C-shape and turn uniformly pink-orange. A perfect prawn curves to a loose C — fully pink with no grey. An overcooked prawn forms an O shape (fully curled) with a rubbery texture. The difference in time between a loose C and a tight O is approximately 45 seconds. Remove from heat at the loose C stage — the residual heat of the broth will finish them.

Nam prik pao (Thai roasted chilli paste) adds smokiness, sweetness from caramelised shrimp paste, and complex bitterness from the roasted chillies. Full-fat coconut milk is essential — the fat creates the emulsified creamy texture. Boiling after adding coconut milk causes the fat to separate and rise to the surface, breaking the emulsion and leaving an oily, unappetising appearance.

From the canon — Nam prik pao (roasted chilli paste) is the essential made-ahead aromatic base that underlies tom yum nam khon, pad thai seasoning, yam neua yang, and dozens … Nam Prik Pao — Roasted Chilli Paste / น้ำพริกเผา →

Lime juice is added off heat because its key aromatic compounds — citric acid esters and volatile terpenes — begin degrading above 70°C, leaving flat sourness without the floral brightness. Fish sauce similarly changes character when boiled, intensifying in saltiness and losing its more delicate umami notes. Both are finishing seasonings, not cooking ingredients. Add in small increments — there is no correcting over-seasoning in a broth.

From the canon — Fish sauce — nam pla — is the universal salt of the Thai kitchen. Fish Sauce (Nam Pla): Selection and Use →

Thai condiment philosophy acknowledges that taste is subjective. The chef balances the soup as a template; the diner perfects it. The table condiments are not a hedge against under-seasoning — they are a cultural acknowledgement that no fixed recipe can account for individual preference. The correct sequence: taste first, add what is needed. In Thailand, the first adjustment is almost always more lime.