Place butter and sugar in a bowl of an electric mixture fitted withthe paddle attachment; mix on medium speed until smooth, about 2 minutes. Mix in eggs one at a time. Stir in vanilla.
Sift flour, cocoa powder, baking soda, baking powder, and salt in to a bowl. Mix into butter mixture on low speed until weel combined. Stir in chocolate, coconut, and walnuts.
Using a 1-1/2 inch ice cream scoop, drop batter onto baking sheet lined with parchment paper, spacing 2 inches apart. Flatten slightly. Bake until set about 10-12 minutes. Let cool on sheets on wire racks 2 minutes. Transfer cookies on parchment paper to racks to cool completely.