10green poblano or Hatch-style chile, like Anaheim
Roast the chiles. I do this over an open gas flame on my stovetop, but it's better done over a ragingly hot, smoky wood fire. You don't want to really cook the chiles, which is why I don't use my broiler or oven, but if this is all you have, go for it -- broil the chiles, turning often. I char the skins of the chiles over the open flame until they are almost universally black.
When you've blackened each chile, put it in the produce bag to steam. When they're all done, let them steam in the bag until cool enough to work with. Remove the skins. I do this by scraping the skins off with a butter knife, from stem towards the point. Do not rinse the chiles, as this removes a lot of flavor.
To dry your chiles, hang them by the stem with the string in a hot, airy, dry place, like a garage in summer, or under a porch. Do not sun dry them, as this will bleach the chiles. Shade is key. Alternatively, you can dry your chiles pasado in a dehydrator set at about 110F, more or less.
There's a trick to this: The section of the chile closest to the stem will take a long time to fully dry. When you hang the chiles, it dries them more evenly. If you are dehydrating, you will need to turn the chiles over a few times. It can take a full day in a dehydrator, up to a week in open air.