In a medium bowl whisk together flour, cornstarch, baking soda and salt. Set aside.
To brown the butter, place butter in a medium, heavy-bottomed saucepan over medium heat and melt. Keep heating just until small golden bits start to appear at the bottom, and the butter smells nutty and caramely. Watch it carefully because the butter can burn quickly at this point. Remove from the heat and immediately pour melted butter into a large bowl and allow it to cool slightly.
Add brown sugar and granulated sugar and whisk until well blended. Add egg and vanilla extract and whisk until combined. Stir in flour mixture, mixing just until combined. Don’t over mix. Fold in chocolate chips.
Drop rounded balls of dough onto prepared baking sheet, the size of 1.5 tablespoons each (I use an ice-cream scoop). Bake for 10-12 minutes, until cookies just begin to brown at the edges, but the center is still soft. Allow to cool in pan for at least 10 minutes or until the cookies are easy to transfer without breaking. Transfer to a wire rack to cool completely.