First, line your cookie sheets with parchment paper for an easier clean-up.
Next, in a large bowl cream together the butter and both sugars for at least 5 minutes, scraping down the sides of the bowl as needed. Then add vanilla extract and large eggs. Mix together for another two minutes until well combined.
In a separate bowl, whisk together the dry ingredients – flour, cornstarch, baking powder, salt, and baking soda.
Stir the flour mixture into the wet ingredients, and mix to combine. Fold in 2 cups of chocolate chips.
Use ½ cup of cookie dough to make each cookie doug ball. Roll the dough into a ball, squish it down slightly, then add a couple more chocolate chips on top. Place the dough balls on the cookie sheet. Try not to crowd them, there should be no more than 6 on a pan. Chill for at least 1 hour or up to 24 hours.
Preheat oven to 375 degrees. Bake the cookies on prepared baking sheets for 15 minutes then check them. They should be golden but not shiny. If they are not baked all the way, they may need a few more minutes.
Allow them to rest on the pan for 15 minutes before removing them, then move them to a wire rack and decorate once completely cooled! Frosting can be spread or piped onto the top of the cookies with a piping bag if desired.