In a medium bowl, whisk together the flour, cornstarch, baking powder, baking soda, and salt. Set aside.

In a large mixing bowl, add the butter and sugars. Beat on medium-high speed until pale and fluffy.

Scrape down the bowl and add in the eggs and vanilla. Beat on medium-high speed for about 3 minutes until pale and creamy.

Scrape down the bowl and mix again.

Dump in the dry ingredients and mix on low-medium speed until almost combined.

Remove the bowl from the stand and add in the chocolate. Fold it in with a rubber spatula, working in the remaining bits of dry ingredients. Do not over mix.

Weigh out each cookie to be 6 oz and shape the dough fairly tall. Place the dough balls side-by-side on a tray. Press extra chocolate chips on top if desired.

Chill the dough uncovered for at least 4 hours or preferably overnight.

To bake, preheat the oven to 350F and place 3 cookies on a large baking sheet lined with parchment paper, ensuring they are well spaced apart.

Bake for 13-16 minutes, or until the edges are pale golden and the center looks dull but doughy.

Remove the tray and gently hit it against the surface to flatten the cookie. Use a fork to adjust any edges if needed.

Sprinkle the warm cookies with sea salt and let them settle on the baking sheet for about 3-5 minutes.

Transfer to a cooling rack and continue to bake the rest of the cookies. Enjoy warm or cooled.