01 -
Using a stand mixer for 5 minutes (or 7 minutes with a hand one), beat together the butter, cream cheese, both sugars, egg, and vanilla until light and fluffy.
02 -
Gently mix the flour, cornstarch, salt, and baking soda into the wet mixture, stopping as soon as everything's just blended—this takes about a minute.
03 -
Carefully fold the chocolate bits or chunks into the dough.
04 -
Scoop the dough into round mounds about 2 inches wide, flatten them slightly, then chill them for at least 2 hours—or as long as 5 days.
05 -
Pop them in the oven at 350°F for 8-9 minutes until the edges are firm but the centers still look slightly underbaked. Let them rest on the baking sheet for about 5 minutes to cool.