Preheat oven to 350F.

In the bowl of a stand mixer fitted with a paddle attachment (or with a hand mixer), cream together butter, brown sugar, and granulated sugar until fluffy. Add egg and vanilla and mix.

Sift in flour, cornstarch, baking soda and salt. Mix until just combined. Fold in chocolate chips using a rubber spatula.

Drop dough, using a tablespoon, onto a prepared baking sheet. Bake for 8-10 minutes, just until the edges start to brown. The insides will not brown.

Transfer the sheet to a wire rack and let cool for about 5 minutes before removing from pan.