Preheat your oven to 350°F (175°C) and prepare a 9x9-inch baking pan lined with parchment paper.

In a mixing bowl, combine flour, baking soda, baking powder, salt, and nutmeg, whisk well and set aside.

In another bowl, cream butter and sugar together until light and fluffy, about 3-5 minutes.

Add the egg, vanilla extract, and buttermilk to the mixture and mix until smooth.

Gradually incorporate the dry ingredients into the wet mixture until just combined; do not overmix.

Transfer the batter to the prepared pan, spreading it evenly, and bake for 18 to 20 minutes.

Cool the pan on a wire rack for about 10 minutes before removing bars using parchment.

While cooling, whisk together powdered sugar, maple syrup, maple extract, and milk until smooth.

Once cooled, drizzle the glaze over the bars and let it set before slicing and serving.