Place the Chicken pieces in a large pot with enough water to cover plus an extra inch. Add the Onion and garlic, and bring to a boil over high heat. Reduce the heat and simmer covered for 90 minutes. Remove the soup from the heat and transfer the Chicken pieces to a plate. When they have cooled, remove and discard the skin from the Chicken. Remove the meat from the bones and cut or shred it into small pieces. Strain the broth through a sieve and return it to the pot. Skim the fat off the surface of the broth and warm over moderate heat. Add salt and pepper to taste.