*Toasting the walnuts is optional but adds a great flavor and really nice texture to the final cookies.
Get Everything Ready
If toasting walnuts do this first so that they're no longer warm when you start the cookie dough.
Preheat oven to 410 degrees and line 2 large baking sheets with parchment paper or Silpat mats.
Cut cold butter into small cubes (about 1/2 inch square) and chill until ready to use.
Measure both flours, cornstarch, baking soda and salt into medium bowl , whisk to combine and set aside
Make Dough
In large mixing bowl cream cold butter and both sugars with electric mixer until smooth and creamy. This will take between 2 and 4 minutes, depending on your mixer
Add vanilla and cold eggs, one at a time, beating to thoroughly mix after each egg. Scrape bowl.
Add flour mixture and beat on low just until combined. You don't want to overmix. You'll need to scrape the bowl a couple of times to make sure all the flour is incorporated.
Add the chocolate chips and walnuts and mix just until distributed evenly.
Divide dough into 8 large balls (if using a scale they'll each be about 7 ounces) and place 4 on each lined baking sheet. DO NOT FLATTEN!
Sprinkle the top of each with a little flakey salt.
Bake in a 410 degree oven 9-12 minutes. They won't flatten out during baking and will look underdone but be golden on the tops. Don't overbake.
Let them rest ON THE WARM BAKING SHEETS for 10 minutes to set before eating.
Enjoy!!!!