Preheat your oven to 350°F (175°C).
Peel and cube the sweet potatoes.
Boil the sweet potatoes until tender, about 15-20 minutes.
Drain and mash the sweet potatoes in a large mixing bowl.
Add granulated sugar, brown sugar, melted butter, eggs, vanilla extract, milk, ground cinnamon, and salt to the bowl.
Spread the sweet potato mixture into a greased baking dish.
Top the casserole with mini marshmallows.
Bake for 25-30 minutes until marshmallows are golden brown.
Remove from the oven and let it cool for a few minutes before serving.