Dried chiles must be cleaned, dry roasted on a comal or iron griddle, rehydrated, and puréed before use in enchilada recipes. The purpose of dry roasting chiles is to caramelize the sugars and release the aromatic oils—not to fully cook them.
How to Prepare Dried Chiles
Directions:
Wipe each chile with a damp cloth to remove any dust.
Using a knife or scissors, cut a slit down the side and remove the seeds, veins, and stem. (It saves cleanup to do this over a sink or bowl to catch the seeds.) Tear the chile into manageable pieces. Repeat with remaining chiles.
With tongs in one hand and a spatula in the other, place a piece of prepared chile on a well-seasoned, unoiled comal or iron griddle over medium heat (comal should not be extremely hot, which would burn the chile and make the sauce bitter). Press on the chile with spatula for a few seconds while holding it in place with tongs. The inside flesh should turn a medium brown color. The skin may or may not blister, depending on amount of moisture in the chile. Turn the chile over and repeat the process on the other side, being careful not to scorch it. Transfer to a bowl, and roast the remaining chile pieces.
When all chile pieces have been roasted, add enough hot water to cover and soak for a few minutes until soft (approximately 15 minutes, depending on how dry the chiles are).
Unless instructed otherwise in a specific recipe, discard the soaking liquid. Place reconstituted chiles in a blender along with a small amount of fresh water (or broth, if called for), and purée to a smooth consistency. Strain the chile purée through a medium-mesh strainer before proceeding with a recipe.
Notes: Do not soak the chiles too long or they will lose flavor.
The soaking liquid is usually discarded—it can be bitter and may contain impurities such as residual pesticides.
Chef Victor Maldonado says when processing dry roasted chiles with other ingredients in a blender, always put the chiles in the blender first. This helps them more fully incorporate into the sauce.