Cut potatoes in 1″ slices. Place in greased 13 X 9 X 2″ pan. Sprinkle with brown sugar and salt. Pour cream over. Bake in moderate oven (350°) 45 minutes. Remove from oven.
Spread marmalade over potatoes; top with marshmallows. Return to oven and bake until marshmallows are lightly browned, 15 to 20 minutes.