Preheat your oven to 425°F (220°C) and line a 12-cup muffin pan with paper liners.
Prepare the streusel by mixing the flour, brown sugar, cinnamon, and salt in a small bowl. Cut in the cold butter until crumbly, then stir in the toasted pecans. Place in the refrigerator while you make the batter.
In a large bowl, whisk together the sweet potato, eggs, melted butter, oil, buttermilk, vanilla, brown sugar, and granulated sugar until smooth and well combined.
In a separate bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, nutmeg, ginger, allspice, and cloves.
Add the dry ingredients to the wet ingredients and gently fold together just until no dry streaks remain. Do not overmix.
Divide the batter evenly among the muffin cups, filling each about ⅞ full for tall bakery-style tops.
Sprinkle the streusel generously over each muffin.
Bake for 5 minutes at 425°F, then reduce the oven temperature to 350°F (175°C) without opening the oven door.
Continue baking for 13–15 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs attached.
Cool the muffins in the pan for 5 minutes before transferring them to a wire rack to cool completely.
If desired, whisk together the glaze ingredients and drizzle over the cooled muffins before serving.