In a blender or food processor, blend chiles pasillas and anchos with tomatoes, onion and garlic. Strain. Heat oil in a stock pot. Pour blended chile mixture into a pot and fry until it thickens and fat rises to the surface. Add epazote. Mix in the boiling broth and long chiles pasillas. Salt to taste and simmer for 25 minutes.
To serve, pour soup into a tureen. Divide tortillas strips among individual bowls. Ladle soup over tortilla strips. Serve chiles, avocado, cheese and creme fraiche in separate bowls, allowing diners to season soup, to taste.
Prepare the garnish: Heat oil in a frying pan and fry tortilla strips until crisp. Drain on paper towels and sprinkle with salt.