Sift together flour, cornstarch, salt, and baking soda.
Add room-temperature soft butter to a microwave-safe bowl( use a large bowl, so that you can make the dough in the same). Microwave butter for 12 seconds. ( imp ref note 1)
To butter add light brown sugar and white sugar. Whisk for 2-3 minutes until it looks pale and light in colour.
Add egg and vanilla extract. Whisk again for 1 minute until the mixture looks light and airy.
Stir in the dry flour mix and fold with a spatula until mixed and no dry patches of flour remain.
Fold in the chopped chocolate/ chocolate chip. Ler the cookie dough mixture rest for 10-15 minutes. ( this lets the flour to get hydrated).
While the dough is resting, preheat oven to 350 F.
Take a medium-size ice cream/cookie scoop and scoop out 60-65 grams of dough for XL giant cookies. Place portioned cookie dough balls on a cookie sheet. These will spread quite a bit when baked, so place them apart.
Bake the cookies for 10-12 minutes or until the edges are very lightly browned. (Giant cookies can take closer to 14 minutes.) The centers will look very soft, but the cookies will continue to set as they cool.
Let the cookies rest on the baking sheet for 10 minutes, then move to a wired rack and let it cool further.