In a medium mixing bowl, whisk together the flour, corn starch, baking soda, and salt; set aside.
In a large mixing bowl, use an electric mixer to cream together the butter, brown sugar, granulated sugar, and banana until light and fluffy. Stir in the vanilla extract.
Mix the flour mixture into the wet mixture just until combined. Fold in the chocolate chips.
Cover the dough in the bowl and refrigerate for 30 minutes.
Preheat the oven to 375F. Line cookie sheets with parchment paper.
Scoop the dough into the prepared cookie sheets to form 24 dough balls, 2-inches apart.
Bake the cookies at 375F for 8-10 minutes until set and lightly golden brown around the edges.
Cool the cookies on the cookie sheets before serving warm.