Combine flour, cornstarch, baking soda and salt in a small bowl. Set aside.
Cream butter, sugar and brown sugar in a mixer on medium speed until light and fluffy, about 5 minutes.
Scrape down bowl and add cream cheese. Mix for 1 minute. Add egg and vanilla. Beat until fully incorporated. Don't overmix.
Stir in flour mixture. Mix just until well combined. Stir in dark chocolate chips.
Cover bowl and place in fridge for 1-2 hours.
Preheat oven to 350 degrees. Scoop heaping tablespoonfuls onto parchment lined baking sheet.
Bake for 8-10 minutes or until soft to the touch and very golden brown.