Place the chicken breasts in one layer in a 13 * 9 baking dish. Sprinkle with spinach, mushrooms, and seasoning (pre-fry fresh mushrooms).
Combine green onion cream cheese, chicken broth, and olive oil. Pour the sauce over the mushrooms. Cover with a sheet of foil without sealing and bake in an oven preheated to 375F for 20 minutes. Then remove the foil and bake for another 20 minutes.
Sprinkle the grated mozzarella over the casserole and cook for another 5-10 minutes, or until the cheese melts and begins to bubble.