Preheat your oven to 350°F (175°C).
Boil sweet potatoes in a large pot until tender, about 15-20 minutes.
Drain the sweet potatoes and return them to the pot.
Mash the sweet potatoes until smooth.
Add brown sugar, milk, butter, vanilla extract, cinnamon, nutmeg, and salt.
Mix until well combined and smooth.
Transfer the sweet potato mixture into a greased baking dish.
Evenly spread the mini marshmallows on top.
Sprinkle chopped pecans over the marshmallows.
Bake in the preheated oven for 30-35 minutes until the marshmallows are golden brown.