Whisk together the flour, cornstarch, baking soda and salt in your electric mixer bowl and set aside.  In a medium bowl, whisk together the cooled butter, both sugars, egg, yolk and vanilla and then scrape the wet mix into the dry, in the mixer.  Mix on medium speed until well combined, then turn the mixer to low, add in the chips and nuts and mix again.

The dough will be very soft…way too soft to portion out and then chill which is my usual way to go.  I recommend smooshing it onto a plate and refrigerating it for about an hour – at this point you should be able to roll it out into even 1 to 1 1/2 tablespoon-sized balls, and then chill again (or freeze for a treat at a later date).  Once the cookies are in ball form, you can chill for as long as you want (but at least another hour would be best).

When you’re ready to get baking, preheat the oven to 350 and line a couple of baking sheets with parchment.  Place the chilled cookie balls a couple of inches apart to fill the pan and bake for 12-14 minutes until the edges are all lightly browned – the centers will likely still be soft looking.  Leave the cookies to rest on the baking sheets for 5 to 10 minutes before removing them to a rack to cool completely – enjoy!