Cook sweet potatoes until almost done. Peel skin from potatoes and mash with a fork. Mix butter, sugar, vanilla, milk and eggs. Beat with a mixer until smooth.
Pour mixture into corning ware with cover. Place covered in oven and cook at 350 degrees for about 25 minutes. Place marshmallows in dish. Continue to cook uncovered at 350 until marshmallows begin to brown. About 15 minutes. If darker, crustier marshmallows are desired you can torch them with a kitchen torch.
Top off with pecans, cinnamon, nutmeg and whatever else sounds good. Maybe more brown sugar and melted butter.
If prepared ahead of time you can warm up at 350 degrees for about 20 minutes. Probably wait to put the toppings on until warm and ready to serve.
Another version is to not mash potatoes but to cut them into 1/2 inch slices and layer them in casserole dish.