Boil a large pot of salted water, then add the cubed sweet potatoes. Cook for about 15-20 minutes or until fork-tender. Drain and set aside.
In a large mixing bowl, mash the sweet potatoes with a fork or potato masher until smooth.
Add the brown sugar, maple syrup, melted butter, vanilla extract, cinnamon, nutmeg, and salt to the sweet potatoes. Mix well until everything is combined and smooth.
Transfer the sweet potato mixture into a greased 9x13 inch baking dish, spreading it evenly.
Sprinkle mini marshmallows on top of the sweet potato layer, ensuring an even coverage. If desired, add chopped pecans or walnuts for added crunch.
Bake in the preheated oven for 25-30 minutes, or until the marshmallows are golden brown and toasted.
Remove from the oven and allow to cool slightly before serving.
Notes
Serve warm, garnished with cinnamon and paired with whipped cream or vanilla ice cream.