Toast chiles on a hot comal or cast iron pan for just a minute or 2 on each side, do not allow to burn. Alow to cool.

Split the chilies and remove the seeds. Soak in hot water for 10 minutes. Remove from the water and puree into a smooth paste. Stores well in a tightly sealed jar, refrigerated for several months.

This method works for any type of chile.  Chipotle chiles (meco) will require a longer soaking time.