Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners or lightly grease it.
In a large bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, ginger, and salt.
In a separate bowl, mix the mashed sweet potato, brown sugar, oil, eggs, vanilla, and milk until smooth.
Gradually add the dry ingredients to the wet ingredients and stir until just combined. Be careful not to overmix.
For the pecan streusel topping, combine the brown sugar, flour, and cinnamon in a small bowl. Cut in the butter with a fork or pastry cutter until the mixture resembles coarse crumbs. Stir in the chopped pecans.
Spoon the batter into the muffin cups, filling each about ¾ full.
Sprinkle the pecan streusel topping generously over each muffin.
Bake for 20-25 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
While the muffins are baking, prepare the glaze by whisking together the powdered sugar, milk, and vanilla until smooth. Add more milk if necessary to reach a drizzling consistency.
Allow the muffins to cool for about 10 minutes, then drizzle the glaze over the top.
Notes
Store muffins in an airtight container lined with paper towels on the bottom to help collect condensation from residual heat in the muffins. Make sure they are completely cooled for best results.The best way to store muffins depends on how soon you want to eat them:
Within 3 days of baking them: Store them on the countertop at room temperature.
In the next few days: Store them in the fridge, but with the risk of a change in texture. Alternatively, store what you’ll eat in the next few days using the countertop method, then freeze the rest.
Within the next 3 months: Store them in the freezer — reheat when you get a muffin craving!