In the bowl of a stand mixer, cream butter and sugars. Add vanilla and egg, mix until incorporated.
In a separate mixing bowl, sift flour, cornstarch, baking soda and salt. Mix in dry ingredients, one cup at a time, until smooth.
Add chocolate chips, fold in.
Place cookies on sheet using a standard scoop. Bake for 8-10 minutes or until edges are golden brown. (Since I made giant cookies I used 2 scoops of dough, patted them together, put 6 on a sheet, and baked them for 14 minutes).
Remove from oven and let cool on sheet for 5 minutes before transferring to a wire rack to cool completely.