In a large mixing bowl, cream together the butter and sugar until light and fluffy. Add the eggs one at a time and mix to incorporate. Add the vanilla and mix thoroughly.
In a separate bowl, combine the flour, bicarb soda, salt and cocoa powder. Whisk together well until combined.
Add the flour mixture to the creamed butter and sugar and mix until completely combined, about 3 minutes. Add the walnuts and chocolate chips and stir in.
Drop by two teaspoonfuls onto an ungreased baking tray. Or roll into balls, place about 5cm apart on the tray and flatten slightly with your fingers.
Bake for 11 minutes. The cookies will appear to be just barely firm with a sheen to their surfaces. Allow to cool on the sheet for about one minute before removing to a cooling rack to cool completely. Store in airtight containers.