Preheat the oven to 410 F (not convection bake). Line the baking sheet with a Silpat or parchment paper

In a mixing bowl, cream together the cold butter and sugars until creamy

Add eggs, one at a time and mix well

In a separate bowl, whisk together both flour, cornstarch, baking soda, and salt. Stir into the butter mixture until just combined; do not overmix. Stir in the chocolate chips and walnuts

Weigh out 3 ounces of dough and mound onto the baking sheet. Do not roll into a ball; keep the dough uneven and rough. A baking sheet will hold 6, 3 ounce dough mounds

Bake 10-12 minutes until the edges are golden brown and top is slightly browned. Let cool for ~10 minutes before eating. Serve warm and may reheat in the microwave for 10-15 seconds on high.