Melt butter in large pot over medium heat. Add onion and cook till soft.
Whisk in flour and cook 1 minute.
Whisk in one carton of College Inn broth and stir until smooth.
Add potatoes, carrots and celery and the second carton of broth.
Bring to a boil over medium heat and cook about 30 minutes or until the potatoes are tender.
Add peas, chicken, milk, salt and pepper and cook another 15-30 minutes, being careful not to let the soup boil.