Place sweet potatoes in a large pot of boiling water. Boil until fork tender, about 15 minutes. Meanwhile, preheat oven to 350 degrees F.
Drain the potatoes and return to pot, away from heat. Mash in the butter, brown sugar, cinnamon and orange juice. Spread evenly in a large greased casserole or 9- x 13- inch pan. Top with marshmallows.
Bake for 25 to 30 minutes, or until marshmallows are golden brown.
Stir in toasted pecans for a new dimension of texture and flavor!