Preheat oven to 400°. Cut tortillas into strips. Place flat on cookie sheet. Bake for 7-8 minutes or until crisp. Chop onion, cut chicken up. Spray a pot with vegetable oil. Add chicken, cook and stir for 3 minutes. Add onion, garlic, chili powder, and cumin. Cook and stir for 2 minutes. Stir in broth, tomatoes, and chilies. Bring to a boil. Reduce heat and simmer for 10 minutes. Divide tortilla strips among 4 bowls. Ladle soup over tortillas. Top with grated cheese and cilantro. Garnish with lime slice if desired.