Preheat the oven to 350°F (175°C).
Peel and cube the sweet potatoes, then boil until tender.
Drain the sweet potatoes and mash them in a large bowl.
Stir in brown sugar, melted butter, eggs, vanilla, cinnamon, and nutmeg.
Transfer the sweet potato mixture to a greased baking dish.
If using, sprinkle mini marshmallows or pecans on top.
Bake for 25-30 minutes, or until heated through and the topping is golden.
Remove from the oven and let cool slightly before serving.