Brown butter, heating in a skillet over medium high heat to melt it down until the bits in the bottom get toasty and golden brown. Continually stir to be sure it does not burn.
Pour it into your mixing bowl and chill until it reached the consistency of room temperature butter
Beat on medium-high speed for 1 to 2 minutes or until light and fluffy and no visible chunks of butter remain.
Add brown sugar and continue to beat for 1 to 2 minutes more.
In another mixing bowl, whisk together flour, cornstarch, and salt until evenly blended.
Add dry ingredients to butter mixture and mix on low speed for 2 minutes.
Add bourbon and vanilla, mix on low speed until mixture comes together into a smooth dough. I had to add 2 teaspoons of water at this point to make a smother dough.
Roll out cookie dough on a floured surface and cut out shapes desired.
Place on a lightly greased cookie sheet
Bake in a preheated 350 degree oven for 12 to 13 minutes
Allow to cool on cookie sheet for 4 minutes then remove to cooling rack to completely cool