Preheat your oven to 350°F (175°C).
Peel and chop sweet potatoes, then boil them until tender.
Drain the sweet potatoes and mash them in a large bowl.
Add brown sugar, melted butter, milk, eggs, vanilla, cinnamon, and nutmeg to the mashed sweet potatoes.
Mix until all ingredients are well combined and smooth.
Transfer the sweet potato mixture into a greased baking dish.
Spread the mixture evenly with a spatula.
Bake in the preheated oven for 25 minutes.
Remove from the oven and sprinkle mini marshmallows on top.
Return to the oven and bake for an additional 5-10 minutes until marshmallows are golden brown.