Preheat the oven to 350 degrees. Line a sheet pan with foil and coat with cooking spray. Prick the sweet potatoes with a fork and place them on the pan in a single layer.
Bake the potatoes until tender, 45 minutes to an hour.
When the potatoes are cool enough to handle, cut them open, scoop out the insides and place the sweet potatoes in a large bowl.
Add the 3 tablespoons of melted butter, milk, brown sugar, maple syrup, cinnamon, egg and vanilla to the bowl.
Use a potato masher or hand mixer to mash or beat the sweet potatoes until mostly smooth.
Coat a 9 inch square pan or 2 quart baking dish with cooking spray.
Spread the sweet potato mixture in an even layer in the pan.
In another bowl, mix together the brown sugar, flour, melted butter and pecans until large crumbs form. Sprinkle the crumb topping over the sweet potatoes.
Bake for 30 minutes or until topping is lightly browned.
Let sit for 10 minutes, then serve.