Preheat the oven to 180°C or 350°F.
In a bowl large enough to take the eggs sugar and eventually the flour. With an electric hand held mixer beat the eggs and sugar untilit becomes light, pale in color and forms a ribbon. You should set the timer and beat this on high speed for 5 minutes. When the eggs and sugar are beaten add the vanilla extract.
Sieve in the flour containing the baking powder and the salt and fold it into the egg and sugar mix. The batter will be pretty thick and sticky.
Add the chopped nuts and chocolate and fold them in.
Take a baking tray or cookie sheet with a sheet of parchment (baking paper) on it and with a rubber spatula scrape out the dough onto the baking sheet trying to form a log about 30 cm. or 1ft long.
If the dough is too sticky - wet your hands – shake off the excess water and try shaping it with your fingers. I find this always messy but wetting my hands does help.
Bake in the middle of the preheated oven for 20 minutes.
Remove from the oven and move to a cooling rack and let sit for only 10 minutes.
With a serrated knife cut the log into slices about 1½ cm. or ¾ of an inch thick. Place on the baking try lined with a clean piece of parchment (baking paper) and bake for a further 5 minutes remove pan turn all the slices over and bake again for another 5 minutes.
The goal is to dry out the biscotti and lightly color them without burning the chocolate. You should get about 16 slices from each log.