In small dry skillet, toast pasillas over medium-high heat, turning frequently, for 3 minutes.
When cool enough to handle, remove stems, break open, remove seeds, and crumble pasillas.
Place about a third of pasillas in small bowl and set aside. Reserve remaining pasillas.
In same skillet, heat about ¾ inch oil.
Add tortilla strips in several batches and fry until crisp and golden. Drain on paper towels. Pour off all but about 2 tablespoons oil.
In food processor, combine reserved pasillas, onion, garlic, mango and tomatoes.
Add blended mixture to reserved oil in skillet and cook over medium high heat 3 to 4 minutes.
Transfer mixture to large saucepan. Add broth and bring to boil. Simmer 20 minutes.
Stir in cilantro.
Season to taste with salt and pepper.
To serve, place a handful of tortilla strips in each soup bowl. Pour hot soup over tortillas, top with cheese and avocado. Or place remaining pasillas, avocado and cheese out separately to be added as desired.