Melt butter, I did this in my microwave for 45 seconds. Be sure to cover with a paper towel when heating the butter in the microwave or it will splatter.
In a small mixing bowl combine flour, salt, baking soda and cornstarch and stir to combine, set aside.
Allow butter to cool to room temperature, then in a large mixing bowl or stand mixer add butter, brown sugar and sugar. Cream using an electric mixer, for one minute or until completely smooth and light.
Beat in eggs and vanilla to butter mixture.
Add flour mixture to the butter and sugar mixture. Mix until well combined.
Cover dough, I used tin foil and set in the refrigerator. Allow to chill for 1 hour, sometimes I am not patient enough and only set it in there for 30 minutes and the cookies are just fine. And to be honest sometimes I don't even chill, I am too hungry.
Preheat oven to 325 degrees.
Scoop dough and place on baking sheet 2 inches apart.
Place in preheated oven and bake for 12 minutes, or until edges are a nice golden brown and center is still soft. Don't over bake! You want a chewy cookie.
Allow to cool for a few minutes, then devour. You may need to make more than one batch they are so that good.