Preheat your oven to 350°F (175°C).
Boil sweet potatoes in a large pot until tender, about 15-20 minutes.
Drain and mash the sweet potatoes in a large bowl.
Add brown sugar, milk, melted butter, vanilla extract, cinnamon, nutmeg, and salt to the bowl.
Mix until smooth and well combined.
Transfer the sweet potato mixture to a greased baking dish.
Spread the mixture evenly in the dish.
Top with mini marshmallows and chopped pecans.
Bake in preheated oven for 30 minutes or until marshmallows are golden.
Remove from oven and let cool slightly before serving.