This interesting recipe comes from the now defunct Gourmet magazine's December 2008 edition. You make your own stock for this one, so the recipe does take some time, but it's well worth it. The addition of sweet potatoes is different, but I actually liked it. I ended up using white rice because that's all I had, but try it with brown, I think it would be better.
Chipotle Chicken Tortilla Soup
3 carrots, coarsely chopped
3 celery ribs, coarsely chopped
2 onions, coarsely chopped
1 whole chicken (about 3 1/2 lb.)
1 head garlic, halved crosswise
3 1/2 qt. cold water
25 cilantro stems
2 Turkish bay leaves or 1 California
3 whole allspice
1 whole clove
1/2 tsp. cumin seeds
1/4 tsp. black peppercorns
1 medium white onion, chopped
2 Tbsp. chipotles in adobo, finely chopped, plus 1 Tbsp. adobo sauce
1 cup short grain brown rice
1 1/2 lb. sweet potatoes, peeled and cut into 1/2-inch pieces
20 (7 to 8 inch) corn tortillas
6 Tbsp. vegetable oil
1 (15 to 19 oz) can black beans, rinsed
2 firm-ripe avocados
2 limes, cut into wedges
1/2 cup chopped cilantro
Make stock: Bring all stock ingredients to a boil with 2 tsp. salt and 1/2 tsp. black pepper in an 8 to 10 qt. heavy pot, thin skim foam.
reduce heat and gently simmer, uncovered, skimming foam occasionally, 2 3/4 hours.
Transfer chicken to a cutting board, then pour stock through fine mesh sieve into a large bowl and discard solids. Reserve 1 cup stock and return remainder to cleaned pot.
Finish Soup: Toast spices in a small dry skillet over medium-low heat, shaking occasionally, until fragrant and a shade darker, about two minutes.
Transfer spices to a blender along with onion, garlic, chipotles with adobo, 2 1/2 tsp. salt and reserved stock. Blend until smooth and spices are ground. (use caution blending with hot liquid)
Add puree to stock in pot along with rice and sweet potatoes and bring to a simmer over medium heat. Simmer, covered, until sweet potatoes and rice are tender, about 45 minutes.
While soup simmers, discard skin and bones from chicken and cut or shred meat into bite size pieces.
Meanwhile, preheat oven to 375 degrees with racks in upper and lower thirds. Stack tortillas and cut into 1/4 inch thick strips, then toss with oil. Spread in one layer on 2 large baking sheets and season with salt. Bake, stirring frequently and switching sheet positions halfway through, until deep golden brown, 20 to 30 minutes.
When rice and potatoes are tender add chicken and beans to soup and simmer, uncovered, until just heated through.
Meanwhile, quarter avocados lengthwise.
Season soup with salt and pepper, serve with lime wedges, cilantro, avocados and tortillas.