In the bowl of a stand mixer or using a hand mixer, cream together the butter and sugars until fluffy.
Add the egg and vanilla extract and mix to combine.
In a separate bowl, mix together the flour, baking soda, cornstarch and salt. Slowly add the dry ingredients to the wet ingredients until just combined.
Using a spatula, fold in the chocolate chips. Cover the bowl with plastic food wrap and place the dough in the fridge to chill for 1-2 hours. The dough should be cold and rather stiff (but still scoopable).
Preheat oven to 350F and line 2 baking sheets with parchment paper.
Scoop 1 1/2 tablespoon portions of cookie dough and roll them into balls. Place them onto the baking sheet, leaving space around each portion to allowing space for them to spread.
Bake for 10-12 minutes or until the edges begin to turn golden brown. Allow the cookies to rest for 5 minutes on the baking sheet and then carefully transfer them to a cooling rack to cool completely. [Note: Be careful not to over-bake your cookies. They should have slightly golden brown edges but they may still look soft in the center when they come out of the oven. They will continue to bake on the pan while they set for the 5 additional minutes.]
Note: Metric ingredient measurements are provided as a courtesy using a third-party calculator and are rounded to the nearest unit. The recipes provided on this site have not been tested with metric measurements and their accuracy cannot be verified.
The nutritional information provided is based on third-party calculations and is an estimate only. Accurate nutritional facts will vary based on the particular brands used, portion sizes, measurement accuracy and more.