Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
   3                    chipotle chiles -- canned in adobo
                        -- sauce, rinse and
                        -- pat dry
   1      tablespoon    corn oil
   1      pound         tomatillos -- husked and halved
   2      teaspoons     corn oil
   1      small         red onion -- chopped
     1/3  cup           cilantro -- fresh, chopped
   1      tablespoon    rice wine vinegar
     1/2  teaspoon      oregano -- dried
                        salt and pepper -- to taste

Preparation:

Puree the chiles in a blender. Transfer to a large bowl. Heat the first measure of corn oil in a large, heavy skillet over high heat. Add the tomatillos. Sauté‚ until browned on all sides (about 7 minutes). Transfer to a work surface. Add the second measure of corn oil to the skillet. Sauté‚ the onion until tender (about 43 minutes). Add the onion to the chile peppers. Chop the tomatillos. Add to the onion and chile mixture. Mix in the cilantro, vinegar and oregano. Season with salt and pepper. Cover. Chill. Bring to room temperature before serving.