Place chicken, onion, celery, salt and pepper in large pot
Add water to cover chicken
Cook over medium heat until chicken is cooked through
Remove just chicken from pot and cool
Remove chicken meat from bone and discard skin
Tear chicken into small pieces and return to broth
Bring mixture to a boil
Mix baking mix and milk and add to broth in tablespoon measurements
Reduce heat and cook 10 minutes
Cover and cook 10 minutes
Serve hot