A dark (sometimes almost black) green chile with a rich flavor that varies from mild to snappy. The darkest poblanos have the richest flavor. This chile is about 2½ to 3 inches wide and 4 to 5 inches long, tapering from top to bottom in a triangular shape. The very best poblanos are found in central Mexico, though they are now also grown in the U.S. Southwest. Fresh poblanos can be found in Latin markets and in many supermarkets. Their peak season is summer and early fall. They're also available canned. Ripe poblanos turn a reddish-brown color and are sweeter than the green. In their dried state they're known as ancho or mulato chiles. Poblanos can be used in a variety of dishes, but are perhaps best known as the chile of choice for chiles rellenos.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.