In a medium bowl, whisk together all-purpose flour, baking soda, cornstarch, and salt until well combined.

In a large mixing bowl, cream together softened unsalted butter, brown sugar, and granulated sugar until light and fluffy.

Mash large ripe banana and add to the creamed mixture, along with vanilla extract. Mix until well blended.

Gradually add dry flour mixture to wet ingredients, stirring gently. Fold in semi-sweet chocolate chips.

Cover the dough with plastic wrap and refrigerate for 30 minutes to firm up.

Preheat your oven to 375°F (190°C) and line two baking sheets with parchment paper.

Drop rounded amounts of dough onto the prepared baking sheets, spacing them 2 inches apart.

Bake for 9-10 minutes until edges are golden brown and centers look set but slightly soft.

Let cool on baking sheets for about 5 minutes before transferring to a wire rack to cool completely.