Line an ungreased cookie sheet with parchment paper or silpat. Set aside.

In a large bowl using a hand-held mixer or stand mixer with paddle attachment, cream the butter and sugars together on medium speed until fluffy and light in color. Mix in egg and vanilla. Scrape down the sides as needed. In a separate bowl, combine flour, cornstarch, baking soda and salt. On low speed, slowly mix into the wet ingredients. Stir in chocolate chips. Dough will be thick and sticky. Cover dough and chill for at least 30 minutes or up to 1 day.

Preheat oven to 350°F.

Once chilled, the dough will be slightly crumbly, but will come together if you work the dough with your hands as you are rolling individual balls. Drop 1 Tbsp balls of dough onto cookie sheet. Press a few more chocolate chips into the dough balls for looks, if desired. Bake for 8-9 minutes, until barely golden brown around the edges. Do NOT cook them longer than 10 minutes. Remove and let cool for 3 minutes on the cookie sheet. If the cookies are too puffy, try gently pressing down on them with the back of a spoon. They *will* slightly deflate as you let them cool. Transfer to cooling rack.

Cookies stay soft and fresh for up to 10 days in an airtight container.