Preheat the oven to 350°F (175°C).
Boil sweet potatoes until tender, about 15-20 minutes.
Drain and mash the sweet potatoes in a large bowl.
Add granulated sugar, brown sugar, milk, melted butter, vanilla, and beaten eggs into the mashed sweet potatoes.
Transfer the sweet potato mixture to a greased baking dish.
In a separate bowl, mix chopped pecans with mini marshmallows for the topping.
Spread the pecan-marshmallow mixture evenly over the sweet potato mixture.
Bake in the preheated oven for 30-35 minutes until golden brown.
Remove from the oven and let cool for a few minutes before serving.