Bring chicken broth, quartered onion, salt and pepper to a boil in a large soup pot. Add chicken breasts then bring back to a boil. Reduce to low and simmer for 20 minutes or until chicken breasts are cooked through.
Remove chicken from the pot and place on a cutting boar. Cut into large chunks then return to the broth. Add quartered carrots and cook until fork-tender, about 6-7 minutes.
Divide soup between four bowls then garnish with lime juice, cilantro, avocado, minced onion and jalapeño. Season with additional salt and pepper to taste.
While these garnishes are optional, they are the star of the dish so I highly recommend them.