If you love pot pie, you will love this soup. It is comfort food in a bowl. Also it's so easy to make it low calorie with skim milk which does not affect the flavor in my opinion. Need lactose free? No problem, just adjust the milk to suit. A great way to get anyone to eat extra veggies. It looks like a lot of work, but it goes together quickly and you can save time with a store bought rotisserie chicken or leftover chicken.
Spray a large soup pot or dutch oven with nonstick cooking spray and saute the onion and celery for 5-7 minutes over low heat until soft. Add mushrooms and saute for another 5 minutes, being careful not to brown.
Add milk and all but reserve 1/3 cup of the broth and bring to a slow boil over medium heat, being careful it doesn't boil over or stick because of the milk.
Add frozen vegetables, seasoning, chicken and return to a boil. Cover and simmer for 20 minutes until vegetables are cooked. Add potatoes and cook about another 5 minutes until all vegetables are done. Add the reserved 1/3 cup of broth to the cornstarch and stir until smooth. Add that to the simmering soup, stirring constantly as you add. Cook 2-3 more minutes until thickened. Adjust seasoning if needed.