Preheat the oven to 350°F. Line two baking sheets with parchment paper and set aside.
In a small mixing bowl, whisk the flour, salt, baking soda, and cornstarch. Set aside.
In a large mixing bowl, add the butter, sugar, and brown sugar until light and fluffy. Add the milk and vanilla and beat again until creamy.
Add about half of the flour mixture to the wet mixture and use a rubber scraper to combine. Add the rest and mix until combined.
Fold in all the chocolate chips and chunks.
Place large balls of dough (~1/4 cup [60 g] each) on your baking sheet. Top each with extra chocolate and a sprinkle of salt. Want them to be extra big? Double the amount of dough and add a few more minutes to the baking time
Bake for 11-13 minutes, until they are baked to your liking. Sprinkle extra salt right when they come out of the oven.