Warmth, aroma and balance
Many Thai curries are first defined by fresh herbs and chilli aromatics. Massaman feels different: dried spices such as green cardamom, cinnamon, cloves, cumin, nutmeg, mace and star anise give it a warm, almost enveloping depth. Which spices are used and in what proportions is part of each recipe tradition.
The dried spices that reached Siam through Persian, Indian and Muslim trading worlds were unusually intense for Thai cooking of the time. In Thailand they were combined with familiar aromatics such as lemongrass, galangal, kaffir lime peel, coconut milk and tamarind. The result developed its own Thai character: less heavy and dominating in spice aroma, and instead more rounded, harmonious and balanced.
That is exactly why the expression “aroma instead of heat” fits so well: the spices should remain clearly noticeable without covering everything else.