Preheat the oven to 350°F.
In a mixing bowl, whisk together the flour, cornstarch, baking soda, and salt for about 20 seconds, then set aside.
Melt the butter halfway in a microwave-safe bowl, then whisk it fully melted.
Pour the melted butter into the stand mixer bowl, add both sugars, and blend on medium speed until well combined.
Mix in the egg and vanilla extract.
Slowly add the dry ingredients on low speed until combined, then fold in the chocolate chips.
Scoop out slightly heaping ½ teaspoon portions of dough and shape into balls.
For a prettier look, press 3-4 chocolate chips on top if desired.
Place the dough balls on two baking sheets lined with parchment paper or silicone mats, spacing them about 1 inch apart.
Bake for 5-6 minutes until the cookies are soft and slightly under-baked, as they will firm up when cooling.
Remove from the oven and let the cookies cool on the wire rack.
Let it cool completely before serving.