This chile is not very common in the United States but is gaining in availability and popularity. It is hotter than the more common chipotle chile with a unique smoky aroma.
Typical preparation of the chile is to stuff it with cheese and deep fry (chile relleno). The chile is also used in sauces.
If your chiles are very dry and not pliable then heat them on a comal until they become flexible. Use a small paring knife and slit them open carefully. Remove the seeds and veins. Cover the chiles in hot water and soak for about 5 minutes. You can taste a bit of the chile and if it is still to hot to your taste and it if is soak a bit longer (about 10 minutes). Dry the chiles and prepare using your favorite chile relleno recipe.
Toast the whole chile on a hot comal or fry pan over low heat, turning to toast evenly on both sides but don't allow them to burn. The toasted chiles can be torn up and added to a blender with other ingredients or cooked in a sauce.
a cast iron comal used for toasting chiles