Step 1: Preheat your oven to 350°F (175°C) and grease a 12-cavity donut pan with non-stick spray or butter.
Step 2: In a large mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, cinnamon, nutmeg, ginger, and salt.
Step 3: In a medium bowl, combine the mashed sweet potato, eggs, sugar, 1/3 cup melted butter, and vanilla extract until smooth.
Step 4: Add the wet ingredients to the dry ingredients and stir gently with a spatula until just combined. Do not overmix.
Step 5: Transfer the batter to a piping bag or a zip-top bag with the corner snipped off. Pipe the batter into the prepared donut cavities, filling them about 3/4 full.
Step 6: Bake for 12-15 minutes, or until the donuts spring back when lightly touched. Let cool in the pan for 5 minutes before transferring to a wire rack to cool completely.
Step 7: In a small bowl, whisk together the confectioners' sugar, maple syrup, 1 tablespoon melted butter, and milk until smooth. Dip the cooled donuts into the glaze and let set on the rack.