With a paddle attachment cream the butter and granulated sugar for 5 minutes on medium speed. Add the butter and vanilla extract. Add the eggs one at a time until fully incorporated, scraping the bowl periodically. Sift the flour twice with the baking powder. Add the flour mixture on low speed and continue until combined. Do not over mix. Add American pistachios and chocolate chunks and scrape down the bowl. Mix on low speed until evenly incorporated.

Place batter on a floured surface. Using a balance bean scale divide the batter into 2-pound portions. Roll each piece to about 4 inches wide and 18 inches long. Place the dough pieces, three to a pan on the parchment paper lined sheet pans. Brush evenly with egg wash and bake in a 375°F / 190°C oven until golden brown, about 17-20 minutes. Cool slightly. Using a chef’s knife and cutting board cut the logs into ¼ inch / 0.6 cm slices. Place slices back onto the sheet pans and toast in an oven at around 200°F / 93°C until dry and crisp.

Notes
All ingredients should be at “room” temperature. 65°F / 18°C to 75°F / 24°C is the optimum range temperature to achieve the optimum creaming. If desired 2 ounces / 56 g of cinnamon can be added as an additional flavoring. Always sift the flour and leavening agent at least twice before adding to a batter. This will help to remove any impurities, aerate the flour and it helps to distribute the leavening agent evenly in the final batter. Use a good quality chocolate. If possible the sliced biscotti’s can be dried very economically in an oven that is switched off for the day. Leave the cookies in the oven overnight. Don’t forget to remove the cookies from the oven before operating the oven the next day. The cookies have an extended shelf-life due to its low moisture contest. Store in airtight containers. However, if the cookies absorb any unwanted moisture, dry again as needed as descript above.