Preheat oven to 200 degrees C.
In a large mixing bowl, cream butter, brown sugar, and sugar for 4 minutes until light and fluffy.
Add eggs and vanilla. Mix for 1 minute longer.
Stir in flour, cornstarch, baking soda, and salt. Mix just until combined. Fold in chocolate chips.
Bake for 9-11 minutes or until the edges just begin to turn a light golden color. Remove from oven and let set for 5 minutes before removing from the cookie sheet.
Credit to our friend Chamali