Preheat the oven to 350 degrees F.

In a mixing bowl combine the dry ingredients: flour, baking powder, baking soda, cornstarch and salt.

In a separate mixing bowl, combine the butter and 1 cup of both of the sugars with a stand up mixer or a hand-held mixer. Mix until the ingredients are light and fluffy.

Then add int the peanut butter, eggs and vanilla. Mix until these ingredients are thoroughly combined.

Reduce the mixer sped to low and gradually mix in the dry ingredients until they are just incorporated. Do not over mix.

Form the dough into round balls with a cookie spoon. Gently roll the dough in the remaining sugar and place them on an un-greased baking sheet. Use a fork to flatten the dough balls and create a criss-cross shape into each cookie.

Bake for 10-12 minutes until the cookies are lightly golden brown.

Cool on a wire rack and enjoy!