Peel and cut sweet potatoes into cubes. Add to large pot and cover with water.
Bring to boil on stove top and cook for 10-15 or until tender.
While waiting for potatoes to cook, Preheat oven to 375 degrees F. Lightly spray a 13x9 baking dish with cooking spray.
Once potatoes are done, drain and add to large bowl. Mash with potato masher.
Add butter, brown sugar, milk, eggs, vanilla and salt and whisk until well combined. Stir in pecans.
Evenly spread mixture into prepared baking dish.
Sprinkle with marshmallows and remaining pecans.
Bake uncovered for 25-30 minutes or until marshmallows are golden brown.