Fresh pasilla chiles (aka chilaca chilies) are a long, slender variety that tends to grow 6”-9” long and about an inch wide. They are slightly sweet with mild to low-medium heat. They often grow twisted or curved and are dark green when young & dark brown when fully mature.
These chilies can be very difficult to find fresh in the US, as they are more commonly used dried in moles, adobos, etc. Fresh poblanos are sometimes mislabeled “pasilla chiles,” but are quite different.
Dried pasilla negro chilies, granulated pasilla chilies, and pasilla negro chile powder are also available.