In a large mixing bowl stir together the pecans, sugar, flour, cinnamon, nutmeg & salt until combined.
Pour in the butter & toss until a crumbly mixture is formed. Set aside until ready to use.
For the pie:
Preheat the oven to 350(f) degrees. Line a baking sheet with parchment paper.
Toss the sweet potato in 2 tablespoons maple syrup & butter until coated. Transfer to the prepared baking sheet & roast until fork tender, about 15 minutes. As the sweet potatoes roast, prepare the pie shells.
On a lightly floured surface roll out prepared pie dough. Cut 4 6-inch rounds & fit them into 4 5-inch mini pie plates. Shape crust as desired.
Line pies shells with parchment, fill with pie weights or dried beans & bake for 15 minutes.
To a food processor add the sweet potatoes, remaining maple syrup, brown sugar, eggs, cream, vanilla, cinnamon, nutmeg & salt. Puree until smooth, about 2 minutes. Scape down the edges as needed.
Evenly divide pie filling amongst the 4 pie pans & sprinkle with the streusel. Bake for an additional 25 to 30 minutes, until the edges are firm but the centre has a slight jiggle. Let cool completely before serving.