With a mixer, cream the butter and sugars together.
Add the eggs, one at a time, mixing until just incorporated.
Add the vanilla.
In a separate bowl, mix the flour, cornstarch, baking soda, and salt together.
Add to the wet ingredients, and mix until just incorporated. Fold in the chocolate chips.
Roll into ⅛ cup balls, and bake on a parchment-lined baking sheet for 9-11 minutes — until the edges are set and peaks are beginning to turn golden.
Let cool on the baking sheet for two minutes before moving to a cooling rack.
Notes
This dough can easily be refrigerated (or frozen!). If you're having issues with the dough spreading (which I don't anticipate, if you follow the recipe), try refrigerating the dough for 30 minutes before baking.
Recipe by The Kitchen Paper at http://c02.ddd.mwp.accessdomain.com/classic-soft-chocolate-chip-cookies/