Combine flour, cornstarch, baking soda, baking powder, cream of tartar, and salt in a mixing bowl. Whisk together and set aside.
Cream butter and both sugars together for about 2 minutes, until mixture looks shaggy.
Add vanilla extract and eggs to butter-sugar mixture and combine thoroughly.
Add flour mixture to butter mixture and blend just until it is incorporated. This is a thick dough.
Stir in chocolate chips.
FOR BEST RESULTS, portion dough into 1-ounce scoops and refrigerate for at least 30-60 minutes. Your cookies will brown better, spread less, and be more flavorful. If you skip this step, they will still be good; just not as good as they could be.
Drop with a heaping tablespoon or 1-ounce portion s coop onto a lightly greased sheet pan.
Bake at 375 for 11-13 minutes or until the bottom is golden brown and brown is developing on top.
Remove from oven and let rest on sheet pan for 2-3 minutes before removing to cooling rack.