1. Preheat standard oven to 400°F. Coat half hotel pan with cooking spray.
2. Sauté onion, mushrooms, ham and garlic in oil in large skillet on medium heat 8 minutes, stirring frequently.
3. Layer half the potatoes, half the vegetable mixture, half the cream and half the cheese in prepared pan. Repeat layers. Cover pan with foil.
4. Bake 30 minutes. Uncover and bake 20 to 25 minutes more or until gratin is bubbly and potatoes are tender with pierced with a fork. Let stand 15 minutes before dividing evenly between 4 plates and serving.
Nutritional information per serving: Calories 568; Total Fat 35g; Saturated Fat 17g;