When ready to bake, preheat oven to 350°F and grease a baking sheet with butter or nonstick spray.
In a large mixing bowl, cream the butter and cream cheese with an electric mixer until smooth. Add the sugars, egg, and vanilla and beat again on medium-high until light and fluffy, about 7 minutes.
Add flour, cornstarch, baking soda, and salt and mix until just combined. Stir in chocolate chips.
Using a medium cookie scoop, scoop out cookie dough and flatten mounds slightly using your palm. Cover with plastic wrap and refrigerate for at least 2 hours.
Once chilled, place cookies on prepared baking sheet 2 inches apart (about 8 cookies per sheet) and bake until edges have set, 8-9 minutes. Cookies will look slightly undercooked and pale in the center; they’ll firm up as they cool.
Allow cookies to cool on baking sheet for 5 minutes before transferring to a wire rack to finish cooling. Enjoy!