In a medium bowl, stir together the ground nuts, flour, cocoa and baking powder; set aside. In a separate bowl, beat eggs on the high speed of an electric mixer, gradually add the sugar and mix until thick and yellow. Stir in the melted butter and vanilla. Gradually stir in the flour mixture, just mixing enough to combine.
Heat up the pizzelle iron until a drop of water dances on the surface, then slightly reduce heat. Drop 1 rounded tablespoon of batter for each cookie. Close the lid and bake for about 2 minutes, depending on your iron. Turn cookie out and trim before cooling on racks.