• In a large bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
• In the bowl of a stand mixer fitted with the paddle attachment, beat the cold butter on medium speed about 1 minute to soften slightly. Add the granulated sugar and brown sugar, and mix until incorporated and fluffy. Add the eggs and the vanilla. Mix on medium-low speed until the mixture looks blended. Turn off the machine and add the dry ingredients. Mix on low speed just until the dough comes together. Turn off the machine and fold in the walnuts and chocolate chips by hand using a rubber spatula. You will have to use some muscle!
• Drop scoops of the dough onto 2 parchment-lined baking sheets; you should be able to fit 6 cookies on each sheet. Place the baking sheets in the freezer for 1 hour. It’s necessary for the dough to be completely frozen when you put the cookies in the oven or they will spread out too much and not have a soft, chewy interior.
• When you’re ready to bake, preheat the oven to 375 F.
• Transfer the baking sheets directly from the freezer to the oven and bake the cookies for 18 to 22 minutes, or until golden brown around the edges and beginning to brown on top, but still slightly underbaked in the middle. Let the cookies cool on the baking sheets for 5 minutes and then transfer them to a wire rack to cool completely.
  

TIP: If you want to make these the dough in advance, you can. Scoop and place on a baking sheet to freeze completely, then place in a ziplock bag. Just bake what you want when you want it!