Bake the clean sweet potatoes in a 425F degree oven until soft in the center. This will take between 40-55 minutes. Check the doneness of the sweet potatoes by inserting a knife in the center, if it's soft it's ready.
Reduce the heat to 350F, then let the sweet potatoes cool down until you can handle them without burning your hands.
Slice the sweet potatoes lengthwise, about 3/4 of the way up. This will remove the top, leaving the flesh of the sweet potato visible. Scoop out the sweet potato and put in it a medium bowl, making sure to leave about 1/4 inch of sweet potato in the skin to help keep the whole thing stable and supported.
Mash the sweet potatoes, add in the butter, maple syrup, salt, and cinnamon, and mix to combine.
Stuff the sweet potatoes with the seasoned mashed sweet potatoes and top with the pecan streusel.
Bake the sweet potatoes one more time for 20-30 minutes or until the filling is hot and the topping is golden and crispy.