Spray medium size casserole dish and set aside. Preheat oven to 375.
Brown hashbrowns until very crispy on both sides. (Use cooking spray - I spray the pan and add the hashbrowns and prior to flipping - I spray the top of the hashbrowns.)
Meanwhile, in a dutch oven, cook turkey, onion and celery until turkey is done and vegies are tender. Add the mushrooms and frozen vegies and cook for about 8-10 minutes (until vegies are tender). If any liquid develops, pour it out.
Pour soup and beef bouillon into the turkey/vegie mixture, stir and cook on medium heat until heated through.
Put the cooked (crispy) hashbrowns in the bottom of the casserole dish (sprayed). Pour the turkey/vegi/soup mixture over the hashbrowns and spread evenly. Add the cheese on top and cook in oven until cheese is melted and dish is heated throughout - 15 minutes or so.
I will admit that I usually will add more cheese but I will count it in my points.