Preheat oven to 350°F. Line two large baking pans with parchment paper. Set aside.
In a large bowl, cream butter, light brown sugar, and granulated sugar until light and fluffy, about 1-2 minutes.
Mix in eggs, peanut butter, and vanilla until combined. Stir in flour, cornstarch, baking soda, and salt until just incorporated. Do not overstir.
Drop 2 tablespoon balls of the dough onto the cookie sheet, about 2 inches away from each other. Flatten each cookie with a criss-cross pattern using a fork so that it is about ½ inch high. I prefer to dip my fork into granulated sugar after every 2-3 cookies to help prevent sticking.
Bake for 8-10 minutes, or until golden brown around the edges. Let cool for five minutes before placing on a cooling rack.
See my tips and tricks for making these Crunchy Peanut Butter Cookies above the recipe box.