In a large bowl, mix together the flour, cocoa powder and baking soda.
In a serarate bowl, cream together the butter and sugars. Add in the eggs one at a time, mixing after each addition. Mix in the vanilla.
Slowly mix the dry ingredients into the wet ingredients until fully incorporated.
Fold in the white chocolate chips, chocolate chips and pecans.
Cover and refrigerate the dough for at least 30 minutes.
Preheat the oven to 350°F. Line two baking sheets with parchment paper.
Using a medium cookie scoop, scoop the batter onto the baking sheets and bake in the preheated oven for 10 minutes. Allow the cookies to cool for around 5 minutes on baking sheets before transfering to wire racks to cool completely.