Preheat the oven to 350 degrees. Line a baking sheet with parchment paper and set aside.
Add the sugar, butter, and vanilla to a mixing bowl and beat on high for 5 minutes. It will be light and fluffy, and lighter in color. Add the bananas, sour cream, and egg. Mix until just combined.
Add the dry ingredients and mix until just combined, careful not to over mix. Fold in the walnuts. Use a 1 1/2"-2" scoop to portion out the muffin tops onto the prepared baking sheet. Bake for 11-13 minutes. The muffin tops will puff up and be a light golden color. Allow to cool completely. Mix together the powdered sugar and maple syrup until smooth and silky. Drizzle with the maple glaze. Enjoy!