Line a baking sheet with parchment paper and set aside.
In a large bowl cream together white sugar, brown sugar, butter and shortening.
Beat in egg and egg yolk.
Stir in vanilla extract.
Mix in peanut butter. Set aside.
In a medium bowl, whisk together flour, cornstarch, salt, baking soda, and baking powder.
Add dry ingredients into wet ingredients just until combined.
Fold in peanut butter chips.
Using a medium cookie scoop, scoop out the dough.
Roll the dough into a smooth ball and place on the cookie sheet 2 inches apart.
Flatten the balls of dough slightly.
Place extra peanut butter morsels into the dough. (for a better appearance after baking)
Bake for 5- 6 minutes or until the edges are golden and the center is slightly underbaked.
Let cookies sit on pan for 4-5 minutes before removing to a cooling rack to finish cooling.
Once cooled, store in an airtight container.
Video
Notes
You can use all butter if needed, I just like the texture shortening gives. Under- bake the cookies and allow cookies to finish cooling on the pan. This will result in a chewy, soft cookie. (baking times will vary based on your oven)