Peel and chop four large sweet potatoes into 2-inch chunks. In a large pot, bring salted water to a boil and carefully add the sweet potatoes. Cook for about 15 minutes until very tender.

Drain the sweet potatoes and transfer to a mixing bowl. Mash until smooth and creamy. Stir in butter, milk, brown sugar, cinnamon, and nutmeg.

Preheat your oven to 400°F (200°C). Grease a 9x13-inch baking dish. Spread the sweet potato mixture into the prepared dish, smoothing the top.

Sprinkle mini marshmallows and chopped pecans over the sweet potato mixture. Press down slightly.

Bake uncovered for 15-20 minutes, watching for the marshmallows to become golden and puffed.

Switch the oven to broil and broil for an additional 2 minutes, watching closely to prevent burning.

Remove from the oven and let sit for 5 minutes before serving. Drizzle with maple syrup if desired.