Line a cookie sheet with parchment paper. Or grease and flour a cookie sheet.
In a small bowl combine flour, cocoa powder, baking powder and salt. Set aside.
Using a mixer, beat sugar and butter together until soft and creamy. About 3-5 minutes. Add eggs and vanilla and mix well. Add the flour mixture and beat until just incorporated. Stir in walnuts.
Remove the dough from bowl and form into a ball. Divide the dough in half and shape into 2 loafs, about 10" x 4" x 1" high.
Bake for 35 minutes until a toothpick inserted in the center comes out dry. Cool for 5-10 minutes and then use a bread knife and gently cut the loaf diagonally into 1" wide slices (I like thicker slices, you can also cut them smaller, about ⅜").
Lay the slices, on their sides (cut side down) and bake an additional 30 minutes or until the cookies are dry and crunch. Cool completely.