Heat a large skillet over medium-low heat and add the olive oil and mushrooms and cook for 5 minutes. Add the baby spinach and stir. Season with the garlic powder, salt and black pepper and cook for 2-3 minutes.
Stir in the Alfredo sauce and chicken breast strips.
In an oven - safe carry out container, cover the bottom with half of the sauce. Add the frozen stuffed shells to the baking dish. Cover the top of the stuffed shells with remaining sauce.
Cover with foil and bake for 30-35 minutes. Remove from oven and sprinkle with Parmesan cheese if desired. Top with carry out lid.
