Heat oven to 400°F. Spray bottom of 12x8-inch (2-quart) glass baking dish with nonstick cooking spray. In sprayed dish, combine potato slices and contents of sauce packet from potatoes. Stir in boiling water until well mixed.
In medium bowl, combine all remaining ingredients; beat with wire whisk until smooth. Add to potatoes; mix well. (Potatoes should be completely covered with cream mixture.)
Bake at 400°F. for 40 minutes or until knife inserted in center comes out clean and top is golden brown. Cool 10 minutes before cutting into squares.