Roasting fresh chiles releases their natural flavor compounds.
Fresh chiles tend to bring bright, floral notes to food. Roasting them breaks down their cell walls, releasing more flavor compounds and caramelizing their sugars, which results in a deeper, nuttier taste. But to capitalize on roasted taste, don’t rub off skins under water. In tests, we’ve found this washes away flavor.
Small chiles can be roasted whole. For large chiles, like poblanos or Anaheims, slice 1/4 inch off the top and bottom, pull the core out, make a slit down one side, and then press the chile flat into one long strip.