In large or medium size pot, add oil, celery and onion. Saute over medium heat until tender. Add chicken broth and heat to low simmer. Add frozen chicken breast. At this point you can decide what temp to cook at depending on when you want to serve. It is recommended to cook over low heat for a few hours, but can cook at medium simmer to speed up the cooking time. Once the broth is at full flavor from the chicken and vegetables turn up the heat to a slow boil. Add the vermicelli and cook for until desired consistency, al dente or more well done. See package directions.