Prepare the dry ingredients: Whisk the flour, cornstarch, salt and baking soda in a large bowl and set aside.
Prepare the wet ingredients: Place the room temperature butter and both sugars into a second mixing bowl and beat together until creamy using either a stand mixer with a paddle attachment or a hand mixer. Scrape down the sides of the bowl and then add the vanilla and eggs one at a time while beating for at least 30 seconds after each egg is added.
Incorporate: Add half of the dry mixture to the wet ingredients and mix on low for about 20 seconds; add the rest of the dry mixture and continue to mix just until incorporated. Use a silicone spatula or wooden spoon to fold in the chocolate chips and chunks.
Chill: Place the batter in the refrigerator and chill for a minimum of 2 hours, or overnight. Tip: to chill the dough faster, divide into 2 separate bowls.
Bake: Center a rack in the oven and preheat to 375 degrees F. Line two baking sheets with parchment paper. Place rounded tablespoonfuls of batter onto each sheet at least 2 inches apart and bake for 11-12 minutes, rotating the cookie sheet once. Remove the from the oven once the edges are just starting to brown and the tops are golden (the middle should still look soft.)
Cool: Let the cookies rest on the baking sheet for 5 minutes, then transfer the cookies to a cooling rack using a spatula. Place the second cookie sheet in the oven to bake (if you're using the same sheet, let it cool before you place the next batch on it.)
Enjoy: Enjoy the cookies while they're warm; there's nothing better! The rest of the cookies can be stored in an airtight container in the fridge for up to 5 days.