Whisk together the flour, baking soda, corn starch, and salt in a medium bowl and set aside.
Cream butter, bananas, and sugars together until light and fluffy (a few minutes on pretty high speed). Beat in vanilla extract until combined.
Stir in the flour mixture just until combined. Stir in chocolate chips.
Refrigerate dough for 30 minutes or more.
Preheat oven to 375F. Line two cookie sheets with parchment paper.
Make 24 cookies, approximately same size onto prepared cookie sheets.
Bake cookies for 12-13 minutes or just until they start to turn light, golden brown on top.
Let cookies cool completely on cookie sheets. Store with parchment between layers.
