Preheat the oven to 350 degrees F. Line a baking sheet with parchment paper or foil.
With a fork, pierce each potato 5 to 6 times in different places around the potato. Place the potatoes on the prepared baking sheet. Bake until tender when pierced with a fork, about 1 hour. Remove from the oven and place on a cutting board. Let rest until cool enough to handle, about 10 minutes.
Cut each potato in half lengthwise. Gently scoop out the flesh and transfer to a bowl, leaving a ¼-inch layer of potato. Return the potato skins to the baking sheet.
Mash the sweet potato in the bowl until smooth. Add the melted coconut oil, maple syrup, cinnamon and nutmeg. Stir well to combine.
Evenly divide the potato mixture between the shells and top with the streusel.
Bake until the streusel is lightly toasted, about 15 minutes. Serve.
The streusel topping:
In a medium bowl, stir together the oats, flour, pecans, cinnamon, nutmeg and salt.
Add the maple syrup and melted coconut oil, and stir until the streusel is coated.