After cleaning, you can turn dried peppers into lively seasonings with four simple steps: seeding (for most large meaty peppers), toasting, reconstituting, and grinding.
Seeding: If your recipe calls for seeding, pull out the stems of large peppers and shake out the seeds. With skinny peppers, slice them open with a paring knife (or tear them lengthwise with your fingers) and wipe out the seeds with a paper towel. I like to butterfly large meaty peppers, such as ancho chiles, to ensure even roasting.
Toasting: Heat a cast-iron skillet or comal over medium to medium-high heat until a drop of water sizzles on contact. With seeded and butterflied peppers, press the cut side against the hot surface with a metal spatula for a few seconds. Turn the pepper over with kitchen tongs and press the second side against the skillet, taking care that the flesh toasts lightly but does not burn. A pleasant roasted pepper aroma is a good cue. Watch closely, especially with smooth, thin-skinned peppers such as guajillos and cascabels, and be prepared to snatch them from the heat if they begin to scorch. Meatier, more wrinkled peppers such as anchos and mulatos are less prone to burning and may take longer to roast evenly. Small whole peppers should be toasted for a few seconds and turned once with kitchen tongs.
Reconstituting: Mexican and Central American cooks typically reconstitute toasted dried peppers to facilitate grinding. In Bolivia and Peru where toasting is not considered a prerequisite, dried peppers are also soaked to soften. To do so, cover the peppers with warm water or broth and let them soak for 15 to 30 minutes or until soft. Alternatively, boil them in water or broth to cover for 20 to 30 minutes, until softened. Drain the peppers, reserving the soaking or boiling liquid for use in grinding or later cooking.
Grinding: Process the peppers in a blender or food processor or grind with a circular motion in a molcajete, the three-legged volcanic-stone mortar used by Mexican cooks. Add small amounts of soaking liquid to loosen as necessary, and grind until you achieve the desired consistency.
