Preheat the oven to 400 degrees F. Bake the potatoes for 1 hour or until tender; remove the peel. Reduce oven temperature to 350°.
In a large bowl, mash the potatoes, then beat with brown sugar, half and half, nutmeg, ginger, and cinnamon at medium speed with an electric mixer until smooth. Spoon the mixture into a 13x9-inch baking dish coated with cooking spray.
Combine the topping ingredients in a small bowl; sprinkle evenly over the potato mixture.
Bake at 350° for 20 minutes or until thoroughly heated.
Notes
To prepare ahead, spoon cooked sweet potatoes in 13x9-inch dish without adding topping. Cover with plastic wrap and refrigerate. When ready to bake, remove from refrigerator and let stand 20 minutes at room temperature. Sprinkle the topping mixture evenly over potatoes, and bake at 350 degrees for 20 minutes or until thoroughly heated.