Sift together flour, cornstarch, baking soda and salt.
In a medium-size mixing bowl using an electric mixer, cream together butter, granulated and brown sugar with vanilla. Beat on medium-high speed until light beige in color, around 2 minutes.
Add eggs, one at a time beating well after each addition. Stop and scrape the side of bowl, periodically.
Lower the speed of the mixer and gradually add sifted dry ingredients until fully combined. After all is added beat for 30-60 seconds.
Mix in chocolate chips by hand. Place into an airtight container and chill for 2 hours or overnight.
To bake: Preheat oven to 350°F. Line 2 baking pans with parchment paper.
Use a 2 oz ice cream or cookie scoop to divide the dough. Place at least 2 inches apart on pan. Press additional chocolate chips from extra ½ cup chips, into dough mounds.
Bake for 12-14 minutes or until lightly golden. Cool on pan for 5 minutes then remove to cooling rack to cool completely.
Store at room temperature in an airtight container.