Place the tomato, stock, pasilla chile, and oregano in a blender. Puree and set aside. (see note #1 below)
1 cup roma tomato, 6 cups chicken or stock, 1 pasilla chile, stemmed, 1 teaspoon Mexican oregano
Place a saucepan or stockpot over medium heat and add oil to coat the bottom. Add the carrot and onion and saute until lightly browned.
1 Tablespoon vegetable oil, ½ cup carrot (about 1 carrot) , ¼ cup onion
Add the tomato-chile puree, salt & pepper. Bring to a simmer and taste for seasoning. Add more if needed.
½ Tablespoon fresh ground pepper, 1 teaspoon kosher salt
Add the shredded chicken and simmer for about 10 minutes to develop flavor.
Serve hot and garnish with the tortilla strips, avocado & cheese. Squeeze some lime juice to taste if desired.