Preheat oven to 350. Spray 25 mini muffin cups with nonstick cooking spray.
Combine pumpkin, brown sugars, milk, oil, egg and vanilla in a large bowl; stir to blend. Add flour, baking powder, cinnamon, nutmeg and salt; stir until just combined. Scoop heaping tablespoons into prepared muffin cups.
Bake 11-12 minutes or until toothpick inserted into centers comes out clean. Cool in pans 5 minutes. Remove to wire rack.
For the Glaze
Melt butter in saucepan. Add powdered sugar and vanilla - it will most likely be thick.. Stir in maple syrup. Add water until desired consistency is reached.
Dip tops of muffins into glaze and let stand until mixture is set.
Sprinkle muffins with cinnamon-sugar mixture, optional.