To begin, toast and chop the walnuts, have ready the zests, grind the pepper and bring butter and eggs to room temperature.
Line two trays with parchment paper or nonstick liners like Exopat. Have ready a large floured surface, a dough scraper and extra parchment paper.
In a medium bowl sift the flours, baking powder, soda, salt and pepper.
In a large bowl, cream the butter. Add sugar and beat until light and fluffy. Add the eggs, beating well, and add the zest and vanilla.
Stir in the dry mixture into the butter mixture, then add the nuts. Do not over mix but also don't leave streaks of flour either. You will have quite a goopy mess.
Tip the dough out onto your work surface. Divide the dough into pieces. Two pieces for large trad. size biscotti, four pieces for smaller, thinner ones.
With floured hands and/or your dough scraper, form into logs about 12 inches long and 2 inches wide, quickly place onto trays about 3" apart, brush off excess flour, and put into the middle of preheated oven. (I say quickly because if you bumble about.
picking the logs up they will fall back onto the board. If this happens, don't worry, just form into logs and try again.).
If you don't want to cook all of the logs, wrap them up in parchment, then saran wrap and freeze.
Cook for about 20 mins (small) or 25 mins (large logs) until they are just turning golden.
Remove from oven, let cool on baking rack for 10 minutes or so -- longer doesn't hurt.
Now put the biscotti logs on a big cutting board, cut them on the diagonal about 3/4" wide, replace on same trays cut side down and place in oven (still 350° F.) for 7-8 minutes or until as hard as you want. I like them like granite so it takes them longer.
Let cool on racks and then store in airtight containers.