01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - In a large bowl, whisk together all-purpose flour, baking soda, baking powder, and kosher salt; set aside.
03 - Using a stand mixer fitted with paddle attachment or a hand mixer, beat cold unsalted butter, brown sugar, and granulated sugar on medium-high speed for 3 to 4 minutes until pale and fluffy.
04 - Add eggs individually, mixing thoroughly after each. Blend in vanilla extract until evenly distributed.
05 - Gradually add dry ingredients to the wet mixture, mixing on low just until incorporated. Avoid overmixing dough.
06 - Fold chocolate chips and chopped walnuts or pecans into the dough with a spatula.
07 - Scoop dough using a large cookie scoop or 1/4 cup, forming 12 portions. Arrange on prepared sheets, spacing evenly.
08 - Bake for 13 to 15 minutes, until edges are golden and centers appear barely set. For gooey texture, do not overbake.
09 - Let cookies rest on baking sheets for 10 minutes. Transfer to wire rack to cool completely.