Pour chicken broth into large saucepan or pot and add uncooked chicken breasts. Boil, then simmer on med-high heat for 15 minutes. Let chicken cool, then shred and set aside for later. You will use the remaining chicken broth for the soup.
In food processor or blender coarsely chop garlic, tomatoes, onion and pepper. Pour tomato mixture and spices into pot with chicken broth. Heat to boiling. Reduce heat; simmer 15-20 minutes.
Season with salt and pepper, if desired.
Serve in bowls; garnish with tortilla strips, cilantro, avocado, chicken and queso fresco.