In a large saucepan, cook the onion and the garlic in the oil over moderately low heat for 5 minutes or until the onion is softened.
Add the chilies, tomatoes with their juice, broth, lemon pepper, Worcestershire, spices, and hot sauce and simmer the mixture for 20 minutes.
In a small bowl, combine the flour with the water and whisk it into the soup.
Bring the soup back to a boil and simmer for 5 minutes.
Add the chicken and simmer for 5 minutes or until it is just cooked through.
Stir in the sour cream and salt and pepper to taste, and garnish each portion with the tortilla strips and the coriander, if desired.