1. Preheat your oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper or grease it well.

2. In a medium bowl, whisk together flour, baking powder, baking soda, and salt.

3. In a large bowl, beat butter and sugar until light and fluffy (2–3 minutes).

4. Add eggs one at a time, then mix in vanilla and maple extracts.

5. Alternate adding the dry ingredients and the milk/sour cream to the butter mixture. Start and end with the dry ingredients.

6. Pour batter into the prepared pan and smooth the top.

7. Bake for 22–26 minutes, or until a toothpick inserted in the center comes out clean.

8. Let cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

9. For the glaze: In a saucepan, melt butter and stir in maple syrup. Remove from heat and whisk in powdered sugar, vanilla, and salt.

10. Spread glaze over the slightly warm bars and let set for 15–20 minutes before slicing.