Preheat oven to 350 degrees F and grease and line a square (9 inch) nonstick baking pan with cooking spray and parchment paper. Set aside.

Melt butter in a stainless steel sauté pan over medium heat.

Once melted, continue cooking and whisk regularly until brown bits start to form and the butter is foaming, golden in color, and has a nutty aroma, about 1-5 minutes.

Carefully pour into a large bowl and let cool slightly, about 10 minutes.

To the cooled brown butter, whisk in brown sugar, egg, egg yolk, and vanilla.

Add flour, cornstarch, baking powder, and salt, and stir with a silicone spatula until combined, then fold in the baking chips.

Spread the batter evenly into the prepared pan, then sprinkle lightly with Maldon sea salt.

Bake for 25–30 minutes (mine took about 28) or until the top and edges are lightly browned and a toothpick inserted into the center comes out with a few moist crumbs. You don’t want to over-bake.

Remove the pan from the oven, and set on a cooling rack to cool for 45-60 minutes.

Lift the blondies out of the pan using the parchment paper, cut into squares, and enjoy!

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