Once you have the stock, set it aside and start the soup. I like to keep my chicken soup very basic: carrots, onions, celery, chicken, dill and parsley (and sometimes a little Tabasco, depending on my mood).
In a large stockpot, saute the mirepoix with some fresh thyme and bay leaves. You'll remove those later, so don't worry about picking off the little leaves.
Once the vegetables have softens, season with kosher salt and pepper and add your chicken stock. Of course, it's fine to add store bought stock to fill in the gaps and if you're really stressed for time, you can use that 100%. Theoretically, you're just strengthening the stock you already have. Let the soup come to a simmer and then add your chicken. I use boneless breast and dice the raw meat before adding it to the soup. Many people roast the chickens first and then pull the meat from that. But I like the idea of poaching the chicken. It remains tender and juicy and to be honest, its less effort.
There is no need for concern over salmonella. Chicken is safe when cooked to 165 degrees. (I pull it from the oven 5-10 degrees less than that because it will always continue to cook while resting.) So add the chicken to the soup, crank the heat and bring it to a boil, then reduce the heat and simmer the chicken until it's cooked through. All of the bacteria will be cooked out of the raw meat in the cooking process, just like it would be done in an oven. Try not to let the soup boil again. Nothing is worse than comforting chicken soup with chewy gummy chicken pieces.
Before serving (or bottling in my case), I add some fresh chopped dill and parsley. And of course, taste, taste, taste. You may not need a lot of salt if you're using store bought stock, but I'm sure you'll need it from homemade stock.
Chicken soup is a global soothing mechanism. Variations differ from country to country. For example in Greece, it'a is traditionally made with lemon and egg, in China it is flavored with ginger, spring onions, soy and sesame, and in Mexico, it is often prepared with cabbage and potatoes and garnished with avocados and cheese.
Obviously, from the variations, this soup is a great base. You can add tomato paste, matzo balls, dumplings, mushrooms, fennel, squash, or anything else to mix things up.