Preheat your oven to 350°F (175°C).
In a medium bowl, whisk together the flour, cornstarch, baking soda, and salt. Set aside.
In a large mixing bowl, cream together the butter and sugar until light and fluffy, about 2-3 minutes.
Beat in the egg and vanilla extract until fully incorporated.
Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined.
Form balls of dough about 1-2 inches in diameter and place them on a baking sheet lined with parchment paper.
Bake for 10-12 minutes or until the edges are lightly golden.
Cool on the baking sheet for about 5 minutes before transferring to a wire rack.
