Combine the flour, baking powder, baking soda and salt in a medium sized bowl. Stir until well mixed. Set aside.
Add butter to the bowl of an electric mixer. Beat on medium speed 1-2 minutes until smooth. Scrape down the bowl.
Add the brown & white sugar to the butter. Beat on medium speed 2-3 minutes until light and fluffy. Scrape down the bowl.
Add the eggs one at a time, beating about 60 seconds between each addition.
Add the vanilla.
Turn your mixer to the lowest speed. Slowly add the flour mixture.
Once the flour is about half incorporated, add the nuts and chocolate chips. Continue to stir until all the flour is incorporated. You may need to do the final stirring by hand.
Remove your bowl from the mixer and cover with plastic wrap. Refrigerate for 2 hours (or overnight).
Preheat oven to 375 degrees F. Line 2 baking sheets with parchment paper.
Scoop your chilled dough into balls about 2/3 cup in size. Do not pack the balls together, just pile the dough onto the cookie sheet. The tops of the baked cookie are not supposed to be smooth. Only place 4 dough balls per sheet so there is enough space.
Bake in preheated over for 13 minutes. Remove from oven and cool on the baking sheet for 15 minutes before eating.
Repeat with remaining dough.
Store leftover cookies in an airtight container. Reheat at 350 degrees for 5-7 to remelt the inside.