Peel and chop sweet potatoes into 1" chunks. Add to a large pot with enough water to cover surface of potatoes and bring to a boil. Cook uncovered at a medium/high heat, boil about until easily pierced with a fork (about 10-15 minutes). Drain and transfer sweet potatoes to a large bowl. Blend with an electric mixer to make it creamy. Preheat Oven to 350˚F.
Add the eggs, melted butter, brown sugar, vanilla, salt, and cinnamon to the sweet potatoes then beat with electric hand mixer until well combined.
Spread sweet potato mixture evenly into a 9x13 casserole dish.
In a medium bowl, combine 1/2 cup brown sugar and 1/4 cup flour. Add the butter and use your hands to rub the mixture together until pea-sized crumbs form. Stir in 1 cup chopped pecans.
Top the sweet potato mixture with mini marshmallows, then pecan mixture topping, then the remaining marshmallows.
Bake uncovered for 20-25 min or until the marshmallows are golden brown.