Preheat oven to 400 degrees. Line a light-colored baking sheet with parchment paper or a nonstick baking mat, if desired.
Cream butter and sugars together until creamy.* Since the butter is still cool it might take a few minutes for the butter and sugar to fully mix together. Add eggs, one at a time, mixing well after each addition. *You can cut the butter into small pieces if you'd like to speed up this process.
Add baking soda, baking powder, salt and flour. Mix until dough forms.
Add walnuts and chocolate chips. Mix.Note: it might be easier to mix the nuts and chocolate chips in by hand.
Portion the dough into 6-ounce balls. Bake 5 cookies on each sheet for 11-13 minutes. The outside of the cookie should be golden and the inside gooey.
Allow cookies to cool completely on the baking sheet.
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Notes
The cookies will continue to set up as they cool. Let them cool for 30-45 minutes before eating. Your patience will pay off!Store cookies in an airtight container or wrap them individually in plastic. Cookies are delicious the next day and can be reheated in the microwave for 10 seconds.To make 3-ounce cookies, bake the cookies for 6-8 minutes.