Whisk together the flour, cornstarch, baking soda, and salt in a medium bowl. Set aside.
In a stand mixer fitted with the paddle attachment, beat the butter and cream cheese on medium speed just until a smooth paste forms. Do not aerate. Add the brown sugar, granulated sugar, egg, and vanilla, and beat on medium-high speed until combined and slightly lightened.
Reduce speed to low and add the flour mixture in 5 to 7 small additions, mixing each just until incorporated.
Add the chocolate chips and mix briefly to distribute evenly. Reserve a small handful to press onto the tops of the dough balls before baking.
Scoop the dough into 2-inch balls using a cookie scoop or ¼-cup measure. Refrigerate at least 30 minutes, up to 3 days, or freeze for up to 3 months.
Preheat the oven to 350°F. Line baking sheets with parchment paper and place dough balls 2 inches apart. Press a few reserved chocolate chips onto the top of each ball.
Bake 11 to 12 minutes, until the edges just begin to show color. Cool 5 minutes on the pan before transferring to a wire rack.
Video
Notes
Creaming: Beat the butter, cream cheese, and sugar only until a smooth paste forms. Over-creaming builds air into the dough and produces a cakey cookie rather than a chewy one. Doneness: Pull the cookies when the edges have the faintest color and the centers still look slightly underdone. They firm up as they cool on the pan. Chilling: Chilling is not required since the butter is not melted, but it produces thicker, chewier results and deepens the flavor. Scoop before chilling so portioning is easy. Storage: Store in an airtight container at room temperature for up to 10 days, or freeze baked cookies for up to 2 months. Raw dough balls can be frozen for up to 3 months; bake straight from frozen at 350°F for 12 to 14 minutes.