In a medium bowl, sift the flour, baking soda, baking powder and salt. Mix well.
In a large bowl with a hand mixer or in the bowl of your stand mixer, beat the butter, granulated sugar, and brown sugar together until light and fluffy.
Add the eggs, one at a time, mixing well after each addition. Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.
Fold in the chopped walnuts and chocolate chips.
Cover the bowl with plastic wrap and chill the dough for 30-90 minutes in the refrigerator.
Preheat the oven to 375°F (190°C) and line a baking sheet with parchment paper.
Using an ice cream scoop or spoon portion out the cookie dough to around 5.5oz each. I used a kitchen scale to be sure the balls were equal in size.
Place onto the prepared baking sheet, leaving a few inches of space between each cookie.
Bake for 12-16 minutes or until the edges of the cookies are golden brown.
Remove from the oven and allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely. Enjoy!