Preheat your oven to 350°F (175°C) and prepare a square baking pan.

In a large bowl, whisk together all-purpose flour, baking soda, baking powder, salt, and ground nutmeg.

Cream together unsalted butter and granulated sugar until light and fluffy, then mix in egg, vanilla extract, and buttermilk.

Fold dry ingredients into the wet mixture until combined; be careful not to overmix.

Pour the batter into the prepared pan and bake for 18-20 minutes.

Allow the bars to cool in the pan for 10 minutes before transferring to a wire rack.

Prepare the glaze by whisking powdered sugar, maple syrup, maple extract, and milk until smooth.

Once cool, glaze the bars and let it set before cutting into squares.