1Preheat oven to 350 F. Wash sweet potatoes and peeled and diced. Put the sweet potatoes in a large pot with enough water to cover. Bring to a boil and reduce to medium heat and cook for 15 minutes until tender. Remove from heat and drain. Mash sweet potatoes with electric mixer. Add butter, sugar, orange juice, and cinnamon and mix well. Put the sweet potatoes into a 9X13-inch baking dish and spread evenly. Bake for 30 minutes and put on marshmallows on top and cook for 15 minutes until the marshmallows are puffed and lightly brown.