Preheat the oven to 350°F. Lightly spray a 9x13 casserole dish with nonstick cooking spray. In a large bowl, combine the potatoes, broccoli, garlic powder, salt, cream of chicken soup, heavy cream, and cheese. Mix well. Pour into the prepared baking dish. Bake uncovered for about 1 hour or until golden brown and the potatoes are tender when pierced with a knife.