From: The Cuisines of Mexico, by Diana Kennedy
Chile Ancho:
The chile ancho is probably the chili most commonly used in Mexico. It is
the ripened and dried chile poblano, wrinkled and a deep reddish-brown color.
After soaking, it becomes a brick-red color. A large, good-quality ancho is
about 5 inches long and 3 inches wide, and it ranges from almost mild to
picante (hot). It is often stuffed. Toasted lightly and torn into small
pieces, it is used as a table sauce, or relish, but more often it is ground
to make the base of a cooking sauce. In Morelia it is confusingly called
pasilla, and I have seen it labeled pasilla in California.
Chile Chipotle:
This is a light-brown chile, with a wrinkled skin that smells distinctly
of smoke. It is in fact the chile jalapeno, ripened, dried, and smoked.
... Its name comes from the Nahuatl chil- ("chile") and poctli- ("smoke").
It can also be spelled chilpotle or chilpocle--all forms are used. The
average chile chipotle is 2 1/4 inches long and less than 3/4 inch wide.
It is very often used whole to season soups and stews, but is probably
most popular of all canned in vinegar or a red adobo sauce. The canned
ones are imported and available in all specialty stores carrying Mexican
foods.
There is no substitute for it.
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As for Japanese chilis (often called jap peppers, which is easy to
confuse with jalapenos if you're not paying attention), these are a
variety developed by the Japanese which are pretty similar to anchos,
although usually smaller. They're also usually easier to get.
Tw