In a medium bowl, whisk together the flour, cornstarch, baking soda, and salt. Set aside.

In the bowl of a stand mixture, beat together the butter, brown sugar, and granulated sugar until smooth. Beat in the bananas and vanilla.

Add the flour mixture and mix until just combined. Fold in the chocolate chips.

Cover the bowl with plastic and chill the dough for at least 30 minutes (this will prevent the cookies from spreading out while baking).

Preheat oven to 375 degrees. Line two to three large baking sheets with parchment paper or coat with cooking spray.

Using a cookie scoop (or tablespoon), drop the dough onto the prepared pans, making 36 cookies.

Bake for 9 minutes, until light, golden brown around edges and on top. Cool the cookies, on the baking pans, for 5 to 10 minutes before serving.

Store leftovers in an airtight container for up to 5 days.