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 again and give it a good mix.

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

Remove the bowl from the stand and fold in the chocolate using a rubber spatula. Do not over mix.

Weigh out each cookie to be 6 oz (or 3/4 cup) and shape the dough so that it's fairly tall. Place the dough balls side-by-side on a tray. Press a few extra chocolate chips on top if desired.

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

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. If the cookies still have a mound in the center after 13 minutes, continue baking for another 2-3 minutes.

Right when you remove the tray, wack it against the surface a couple of times to flatten the cookies. Use a fork to push in any edges that look wonky.

Sprinkle the warm cookies with a bit of 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.