Fresh sweet potatoes, cooked until soft and then peeled, can be substituted for the vacuum packed ones. Don't use drained, canned in syrup as they are too moist. Preheat oven to 350. Put sweet potatoes in a large heavy saucepan and cook over medium heat, stirring frequently, until heated through. Mash sweet potatoes. Add sugar, bourbon, butter and vanilla; beat until well blended. Turn into a 2 litre , shallow baking dish. Sprinkle marshmallows over top. Bake, uncovered, 30 minutes, or until marshmallows are golden.