01 -
Using a stand mixer with the paddle attachment, combine butter, cream cheese, light brown sugar, granulated sugar, egg, and vanilla extract. Beat on medium-high speed until creamed, light and fluffy, roughly 5 minutes (or 7 minutes using a hand mixer).
02 -
Stop and scrape down the sides of the mixing bowl. Add the flour, cornstarch, baking soda, and optional salt, and mix on low speed until just combined, about 1 minute. Avoid overmixing.
03 -
Fold in the chocolate chips and chunks by hand, or mix briefly with the mixer, until evenly distributed.
04 -
Using a medium (2-inch) cookie scoop, shape the dough into heaping mounds (about 28 total cookies). Flatten slightly with your palm, place on a plate, cover with plastic wrap, and refrigerate for at least 2 hours or up to 5 days. Do not bake warm dough as it will spread excessively.
05 -
Preheat oven to 175°C (350°F). Line a baking sheet with a silicone baking mat or lightly spray with non-stick cooking spray. Arrange chilled dough mounds on the baking sheet, spacing them at least 2 inches apart.
06 -
Bake cookies for 8 to 9 minutes, until edges are set and tops are just beginning to set. Do not overbake; cookies may appear glossy or slightly undercooked. Remove from heat as they firm up while cooling.
07 -
Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
08 -
Store cooled cookies in an airtight container at room temperature for up to 1 week, or freeze for up to 3 months. Unbaked dough can be refrigerated for up to 5 days and baked as needed.