Bake sweet potatoes in oven for about an hour. Bake until fork tender. Mash sweet potatoes with butter and a few drops of heavy cream to taste. Make sure not to add too much cream. You do not want the mixture too runny. Beat mixture with beaters. Cut oranges in half. Clean out orange shells. set aside some of the orange juice. Mix some orange juice into the potatoes for flavor. Spoon the potatoes into the orange shells. Put a slice of butter on top of the potatoes and sprinkle with brown sugar. Cook in oven until the sugar and butter melt.