This is a very easy and flavorful recipe from Rick Bayless's Everyday Mexican cookbook (which has tons of really good dishes - much simpler than some of his other cookbooks). I have added a teaspoon or so of cumin to this for extra zip, and have doubled the chile amount too without injuring my delicate tastebuds. Last time I made this, I sort of burnt the chile, and it actually tasted quite good, deeper and darker with a bit of tobacco...
Earthy dark pasilla chile (sometimes called negro)... its unique flavor defines tortilla soup in central Mexico. In Michoacan, in west-central Mexico, it's ancho chile. In your kitchen, it might turn out to be another chile, like New Mexico or even a little smoky chipotle (be forwarned that chipotle will make the broth quite spicy).
Makes 10 cups, serving 6
1 large dried pasilla (negro) chile, stemmed and seeded
One 15-oz can diced tomatoes in juice (preferably fire-roasted)
2 tblsp vegetable or olive oil
1 medium white onion, sliced 1/4 inch thick
3 garlic cloves, peeled
2 quarts chicken broth
1 large sprig fresh epazote, if you have one
4 (about 1-1/4 lbs total) boneless, skinless chicken breast halves, cut into 1/2 inch thick cubes
1 large ripe avocado, pitted, flesh scooped from the skin and cut into 1/4 inch cubes
1-1/2 cups (6 oz) shredded Mexican melting cheese, or Monterey Jack, brick or mild cheddar
A generous 4 cups (about 6 oz) roughly broken tortilla chips
1 large lime, cut into 6 wedges, for serving
Quickly toast the chile by turning it an inch or two above an open flame for a few seconds, until its aroma fills the kitchen. (Lacking an open flame, toast it in a dry pan over medium heat, pressing it flat for a few seconds, then flipping it over and pressing it again.) Break the chile into pieces and put in a blender, along with the tomatoes with their juice. (A food processor will work, but it won't completely puree the chile.)
Heat the oil in a large (4 quart) saucepan over medium-high. Add the onion and garlic and cook, stirring frequently, until golden, about 7 minutes. Scoop up the onion and garlic with a slotted spoon, pressing them against the side of the pan to leave behind as much oil as possible, and transfer to the blender; set the pan aside. Process until smooth. Return the pan to medium-high heat. When it is quite hot, add the puree and stir nearly constantly until thickened to the consistency of tomato paste, about 6 minutes. Add the broth and epazote if using. Reduce the heat to medium-low and simmer for 15 minutes. Taste and season with salt, usually about a generous teaspoon (depending on the saltiness of the broth).
Just before serving, add the chicken to the simmering broth. Divide the avocado, cheese and tortilla chips among the serving bowls. When the chicken is done, ususally about 5 minutes, ladle the soup into the bowls. Pass the lime separately. Rotisserie or grilled chicken can stand in for the raw chicken breasts (add it at the last second).