Preheat the oven to 410 degrees. Line 2 baking sheets with silicone mats or parchment paper.
In your mixer bowl, cream together the cold, cubed butter and both sugars for approximately 3 minutes. (I used my KitchenAid mixer with the paddle attachment.)
Beat in the eggs, one at a time, scraping down the sides in between.
Add the vanilla.
In a separate bowl, whisk together the flour, cornstarch, baking soda and salt.
Add it to the creamed butter, sugar and egg mixture and stir until just combined.
Mix in the chocolate chips and walnuts.
Using a large cookie scoop, separate the dough in to 12 equal size balls of dough, yes they are HUGE. (Don’t squeeze the dough together or refrigerate the dough before baking. You want to just lightly form the balls of dough and pop them straight in the oven.)
Place six balls of dough on each cookie tray.
Bake for 11-12 minutes until the cookies are light golden brown on the top. (For best results I cook one tray at a time on the middle shelf.)
Remove from the oven and let the cookies sit on the trays on a cooling rack for 10 minutes, then transfer the cookies to the cooling racks.
Let cool at least another 10 minutes before eating so they set.