Preheat oven to 300 degrees.
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.
Makes 16 1" slices or about 30 ⅜" slices.