Preheat the oven to 350°F. Line a baking sheet with parchment paper and set aside.

Mix the butter and peanut butter in the bowl of your stand mixer fitted with the paddle attachment for 1 minute on medium speed until smooth.

Add in both sugars and mix for 2 minutes until pale in color and fluffy, scraping the sides of the bowl as necessary.

Add in the egg and vanilla and continue mixing for 45 more seconds until combined and smooth.

Add in the cornstarch, baking soda, baking powder, and salt and mix for an additional few seconds until combined.

Turn the mixer to low and add in the flour, mixing until dough comes together. Stir in chocolate chips evenly.

Using a medium (2-tablespoons) cookie scoop dough onto the prepared baking sheet, placing scoops 2 inches apart.

Bake the cookies for 9-10 minutes until they are golden at the edges.

Remove the pan from the oven and allow cookies to cool on the baking sheet for 2-3 minutes and then transfer them to a wire rack to cool completely.