Toasting dried chiles on a comal — timing, temperature, the point of over-burn

Pre-Columbian Mesoamerica. The comal is the universal cooking surface of Mexican cuisine; chile toasting is documented in colonial-era sources describing pre-Columbian cooking.

Toasting dried chiles on an ungreased comal is the technique that unlocks their flavour complexity before soaking and blending. The heat from the comal surface volatilises the chiles natural oils, creates controlled Maillard browning on the chile skin, and softens the dried flesh just enough to facilitate hydration. Correct toasting: heat the comal to medium-high (a drop of water should evaporate immediately). Open the dried chile by tearing off the stem and shaking out most of the seeds (leave a few for flavour). Press the chile flat on the comal, skin side down, with the back of a spatula. Toast for 15–30 seconds per side — the chile should blister slightly, release a fragrant, complex aroma, and darken slightly in colour without turning black. The aroma is the guide: a well-toasted chile smells of chocolate, dried fruit, and smoke. An over-toasted chile smells of ash and bitter carbon — this is the point of no return. Over-toasted chiles make the entire sauce bitter and must be discarded; under-toasted chiles produce a flat, one-dimensional sauce.

Toasting creates Maillard products from the chiles natural sugars and volatilises aromatic compounds in its essential oils. The difference in flavour complexity between a toasted and untoasted chile used in the same recipe is dramatic.