Line 8 x 8-inch baking pan with parchment paper and spray with cooking oil. Preheat oven to 350 degrees F.

In saucepan with a light-colored bottom, melt butter over medium-high heat. Wait for it to bubble, crackle and foam. It will quickly get dark in color and become fragrant. Immediately pour into heat-safe bowl and let cool 5 minutes.

Into slightly cooled browned butter, add sugars and whisk until mostly dissolved. Add eggs and whisk until mixture is shiny with a thick, sticky consistency. (Note: Do not skip this step. It gives the blondies their shiny, crackly top.)

In separate bowl, stir together flours, baking powder and salt. Add dry ingredients to butter mixture along with butterscotch chips, rolled oats and chopped pecans. Stir until combined. (Note: Mixture will be thick.)

Evenly spread mixture into prepared pan. Bake about 28 minutes until top is golden and the sides begin to pull away from pan. While warm, top generously with sea salt, if using. Let cool completely before slicing.