01 -
Preheat the oven to 350°F (175°C). Line a sheet pan with foil and coat with cooking spray. Prick the potatoes with a fork and place them on the pan. Bake until tender, 45-60 minutes.
02 -
When the potatoes are cool enough to handle, cut them open, scoop out the insides, and place in a large bowl. Add butter, milk, brown sugar, maple syrup, cinnamon, egg, and vanilla to the bowl. Use a potato masher or hand mixer to mash until mostly smooth.
03 -
Grease a 9-inch square pan or 2-quart baking dish with cooking spray. Spread the sweet potato mixture evenly in the pan.
04 -
In another bowl, mix brown sugar, flour, melted butter, and pecans until crumbly. Sprinkle the crumb topping over the sweet potatoes.
05 -
Bake for 25-30 minutes or until topping has lightly browned.
06 -
Remove from oven, sprinkle marshmallows on top, then return to the oven. Bake for an additional 3-5 minutes or until marshmallows are just melted.
07 -
Serve immediately.