Serve soup garnished with a generous amount of fresh Pico de Gallo, (again, this is a required component of the soup!)
Optional toppings include shredded cheddar cheese, crumbled corn tortilla chips, and avocado slices.
*You can also cook your own chicken if you don't have any rotisserie chicken on hand. Add 1 tablespoon oil to a large soup pot over medium heat. Sprinkle generous salt on 3 large chicken breasts (1 pound raw chicken). Add it to the pot and brown for 4-5 minutes per side, or until they are no longer pink. Remove chicken from pot to a plate and shred with 2 forks. Set aside. Continue with the recipe in step 1 by adding the onions to the pot, only adding a bit more oil if necessary.
Source: adapted from my mother-in-law Kris, who got it from "Top Secret Restaurant Recipes" by Todd Wilbur.