Cream the butter, shortening and sugar.
Add the eggs one at a time, scraping the bowl each time.
Add the vanilla & Sherry.
Mix all the dry ingredients together in a separate bowl.
Add the dry ingredients in in two batches till well mixed.
Transfer the dough to a table and divide the dough into three equal pieces.
Shape each piece into a log about 10” in length.
Flatten slightly.
Bake the logs at 300 degrees for 20 minutes in a convection oven (350 for 30-35 in conventional).
Cool the log and slice them in 1” thick slices once cool.
Now lower the oven temperature 50 degrees and bake on the biscotti a second time for 20 minutes on each side, turning the biscotti over after the first 20 minutes.
Once cooled, dip in chocolate laced with Messina Hof port.