Whisk together flour, cornstarch, baking soda, and salt in a bowl; set aside.
Whisk melted butter with brown sugar and granulated sugar until smooth.
Whisk in the egg and vanilla extract until glossy.
Fold the dry ingredients into the wet mixture until just combined.
Fold in the mini chocolate chips.
Chill the dough for 15-20 minutes for easier shaping.
Preheat oven to 350°F (175°C) and line baking sheets with parchment paper.
Scoop rounded half-teaspoons of dough and roll into small balls; place 1 inch apart.
Bake for 6-7 minutes until edges are just set; they will look slightly underbaked in the center.
Cool on the tray for 5 minutes before transferring to a wire rack.
