Preheat the oven to 190°C / fan 170°C. Line one or two baking sheets with baking paper.
In a large mixing bowl, beat the butter, sugars, and salt until creamy, about 3 minutes.
Add the eggs, one at a time, mixing well after each addition.
In a separate bowl, whisk together the flour, baking powder, and baking soda. Add to the wet ingredients and mix until just combined. Fold in the walnuts and chocolate chips.
Divide the dough into 8 rough balls, about 160-170g each. Shape them loosely into balls.
Place on the lined baking sheet, spacing them apart.
Bake for 14-16 minutes, until the tops are golden brown with lighter patches. Let the cookies set on the hot tray for at least 10 minutes before moving them - this allows the centers to firm up.
Allow to cool down completely, and store into an airtight container.