In a medium size bowl, whisk together flour, cornstarch, baking soda, and salt. Set aside.
In a large bowl using an electric mixer, cream together butter and sugars on medium speed, about 2-3 minutes. Add egg and vanilla extract; mix until combined.
Slowly add flour mixture to wet ingredients; mix just until combined. Do not overmix.
Cover bowl and refrigerate dough for 60 minutes or overnight.
Preheat oven to 350F degrees.
Scoop dough into 2 teaspoon balls, or use a #60 disher to scoop balls of dough. Place on an ungreased baking sheet or silicone mat/parchment paper lined baking sheet. Keep dough chilled in between batches.
Bake for 7-9 minutes or until barely golden brown around the edges. Do not overbake; the tops will not brown. Cookies may appear to be soft and undone, but they will set as they cool.
Cool cookies on a baking sheet on a wire rack for 5 minutes; transfer to a wire rack to cool completely. Eat & Enjoy!
Notes
BEST Chocolate Chip Cookies should be stored in an airtight container and will keep 5+ days.