2.)Line a baking sheet with parchment paper or a silicone mat and set aside.
3.)Add the butter and peanut butter into the bowl of your stand mixer fitted with the paddle attachment. Turn the mixer onto medium speed and mix for 1 minute, or until smooth and combined. Add both sugars and with the mixer still on medium beat the mixture 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
4.)Add in the cornstarch, baking soda, baking powder and salt and mix for an additional few seconds until combined
5.)Turn the mixer to low and add in the flour, mixing until the dough comes together. Stir in the peanut butter chips evenly.
6.)Using a medium cookie scoop (2 tablespoons) scoop the dough onto the prepared baking sheet, placing the scoops 2 inches apart.
7.)Garnish with extra peanut butter chips, if desired.
8.)Bake the cookies for 9-10 minutes until they are golden at the edges.
9.)Remove the pan from the oven and allow the cookies to cool on the baking sheet for 4-5 minutes and then transfer them to a wire rack to cool completely