Blondies: Preheat oven to 350 degrees F. Lightly spray a 9x9 inch non-stick baking pan with cooking spray.
In a large bowl, add the flour, baking soda and salt. Whisk to combine.
In stand mixer or large bowl, add the sugars, butter, egg whites, applesauce and butter extract. Whisk for 4 minutes, or until creamy, light and appears slightly fluffy.
Add the dry ingredients into the wet ingredients in two additions. Mix until the batter is just combined.
Fold in white chocolate chips. Add the batter to the prepared baking pan. You may need to smooth out the batter to make it even.
Bake 27-28 minutes, until the edges are light brown and a toothpick inserted comes out clean. Don't over-bake the bars as you want them chewy! Remove from the oven and let cool completely in the pan.
Frosting: Meanwhile, in a small skillet, add the butter. Cook on medium heat until it starts to bubble. Swirl the pan occasionally to be sure the butter is cooking evenly. As the butter melts, it will begin to foam. Once you smell that nutty aroma, 1 - 2 minutes, take the pan off the heat and transfer the browned butter into a heat-proof bowl to cool.
In a medium bowl, mix the cream cheese and powdered sugar with a hand held mixer. Start on a low speed then gradually increase to medium, until mixture is smooth. When the butter is cooled, add the maple syrup, butter and a salt. Mix well.
Spread over the cooled blondies. Cut in 16 squares and serve.
Store in refrigerator, in an air tight container.