In a medium mixing bowl, blend your butter with a hand mixer for about a minute, until smooth and creamy. Then add the sugars and cream together with the butter for an additional 2 minutes, until fluffy and light in color.
Mix in the vanilla extract and the egg. Set aside.
In a separate mixing bowl, whisk together the flour, cornstarch, baking soda and salt. Then adding a little at a time, add the flour mix into the wet ingredients while mixing with the hand mixer. Dough will be thick.
Fold in the chocolate chips, then cover bowl tightly with aluminum foil or plastic wrap and refrigerate for at least an hour and up to 2 days.
Once refrigerated and ready to bake, remove bowl from fridge and let dough sit at room temperature for 10 minutes. Preheat the oven to 350F. Line baking trays with parchment paper.
Roll dough into balls, about 1 tbsp. of dough each. Dough will be crumbly but will come together as you work it with your hands.
Bake 8-9 minutes. Cookies should be barely golden brown around the edges and will look soft in the centers. Cook for 5 minutes on the baking tray, then remove to a cooling rack.
Store at room temperature for up to 1 week.
Could also stop at Step 6 and freeze the unbaked dough balls for up to 3 months. Do not thaw to bake, just cook an additional 1-2 minutes.
