In a large mixing bowl using a electric hand mixer or stand mixer with the paddle attachment, cream together your butter, brown sugar, and sugar, until pale and fluffy. Scrape down the sides of the bowl as needed.
In a medium bowl, whisk together your flour, cornstarch, baking powder, baking soda, and salt. Pour your dry ingredients in to your butter and sugar mix, continue to beat on low until it’s almost combined.
Add in the chocolate. Using a rubber spatula, fold your chocolate in to your cookie dough and work in the remaining bits of dry ingredients. Do not over mix.
Line a large baking sheet with parchment paper, using a large cookie scoop place balls of cookie dough on your prepared baking sheet. If desired, press a few extra chocolate chips on to the top of each cookie dough ball.
When ready to bake, preheat your oven to 350 degrees F. Line another large baking sheet with parchment paper for baking. Place 4-5 cookies on your baking sheet lined with parchment paper. Make sure they’re well spaced apart.