Step 1Place the chiles on a rack over the flame on top of the stove. Char the chiles on all sides, then put them in a paper bag and close. (You can also set them under the broiler to blacken the skins.) Let them stand until the skins are easy to peel, about 15 minutes. Remove the stem, seeds and charred peel from the peppers. Chop the peppers.
Step 2Cook the garlic and onion in a 5-quart saucepot sprayed with nonstick cooking spray until the onion is tender and begins to brown around the edges, 3 to 4 minutes. Add the chopped peppers. Cook 1 minute.
Step 3Stir in the chicken broth and add the cubed potatoes. Bring to boil. Reduce the heat to a simmer. Cover the pot and cook until the potatoes are tender, about 20 minutes. Puree the soup in batches with the cilantro and cumin.
Step 4Cook the almonds and pumpkin seeds in a skillet sprayed with nonstick cooking spray and butter until the nuts begin to lightly brown. Spoon the soup into bowls and sprinkle the nuts and seeds over the top.