Start by peeling and chopping sweet potatoes. Place in a pot and cover with water. Bring to boil over medium heat and cook until potatoes are soft. Drain well (see note).
Preheat oven to 375 degrees F. Butter a 2-quart casserole dish and set aside.
Place cooked potatoes in large mixing bowl. Add brown sugar, butter, spices, salt, vanilla and eggs and mash with potato masher or whip with hand mixer.
Spread the mixture in prepared casserole dish. Top with ¼ cup of brown sugar, sprinkling it evenly over the top.
Layer marshmallows in a single layer on top.
Bake casserole for 12 to 15 minutes OR until the marshmallows are golden and toasted and the sides are bubbling. I always place it under the broiler for just 2 minutes to toast the topping just a bit more. You have to watch it carefully so it won't burn.
Cool casserole for at least 10 minutes before serving.
Video
Notes
To make ahead: Cook potatoes till soft, cool completely, then mix with remainingingredients. Spread mixture in buttered dish and cover the dish with saran wrap. Store inthe fridge. Wait to top it with marshmallows (or pecan brown sugar topping) just beforebaking, for best results. After you take the casserole out of the fridge, let it sit in a roomtemperature for 30 minutes. If you take it from a cold fridge to a hot oven, the dish mayshatter.Drain cooked potatoes well, to prevent the water from collecting at the bottom of thecasserole.