Preheat your oven to 350°F (177°C) and line a 9x13 inch baking pan with parchment paper, greasing it lightly.

Cream together the softened unsalted butter and granulated sugar until light and fluffy, about 3-5 minutes. Add eggs one at a time, then mix in buttermilk and vanilla extract until smooth.

In a separate bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. Gradually mix this dry mixture into the wet ingredients until just combined.

Spread the batter evenly in the prepared pan and bake for 22-28 minutes or until golden and a toothpick comes out clean.

Whisk together powdered sugar, maple syrup, and milk in a medium bowl until smooth. Adjust milk as needed for desired glaze thickness.

Let the bars cool for about 10 minutes, then spread the glaze generously over the top while still warm. Cool completely before slicing into squares.