Preheat oven to 350 degrees. In a large bowl, combine butter and sugars and mix with a hand mixer until light and fluffy. Add vanilla and eggs.
In a separate bowl whisk together baking soda, salt, flour, corn starch, and oats. Slowly mix dry ingredients into wet ingredients until just combined. Add peanut butter and mix well. Stir in chocolate chips and spread evenly.
Scoop 1 1/2 inch dollops onto an ungreased cookie sheet. Bake 8-10 minutes until edges begin to brown and centers are barely set. Remove from oven and allow cookies to cool on sheet for 2-3 minutes before transferring to a cooling rack.