Preheat your oven to 350°F (175°C) and line a 9x13 inch baking pan with parchment paper.

In a large mixing bowl, combine unsalted butter, granulated sugar, and light brown sugar. Beat with an electric mixer on medium speed for about 3-5 minutes until light and fluffy.

Add the large eggs one at a time, beating well after each addition until smooth.

Pour in the pure maple syrup and vanilla extract, mixing until well combined.

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

Gradually add the dry ingredients to the wet mixture, alternating with milk and sour cream, stirring gently until just combined.

Pour the batter into the prepared baking pan, spreading it evenly with a spatula.

Bake for 20-25 minutes until a toothpick comes out clean.

Let the bars cool completely in the pan on a wire rack.

Prepare the glaze by whisking together powdered sugar, additional maple syrup, milk, salt, and extra vanilla extract until smooth.

Drizzle the glaze over the cooled bars and allow to set for a few minutes.

Slice into squares or rectangles and serve.