Peel and cube sweet potatoes, and cover with water in a medium saucepan. Bring to a boil over medium-high heat, and cook for 15-20 minutes, or until very tender.
In the meantime, preheat oven to 350°F and lightly grease a small casserole dish or loaf pan.
Drain sweet potatoes and add all ingredients save for the toppings. Mash thoroughly with a potato masher, or use a food processor for a completely smooth texture.
Spread mixture into prepared pan.
Bake casserole for 25 minutes. Top with marshmallows and return to oven for an additional 5-8 minutes, until marshmallows are melted and slightly toasted.