Preheat oven to 325. Place sweet potatoes on microwavable plate. Microwave on high 8 minutes, turn potatoes over and continue microwaving 9-10 minutes or until very tender. Let stand 5 minutes.
Cut potatoes in half, lengthwise. Scoop pulp into large bowl; discard skins. Add cream cheese, brown sugar, cinnamon, and nutmeg to potatoe pulp. Mash with potatoe masher to desired consistancy. Spoon into 9 inch square baking dish.
Mix cereal and butter in medium bowl until well blended. Stir in marshmallows, sprinkle evenly over potatoe mixture.
Bake 30-35 minutes or until topping is golden brown and mixture is heated through.