Begin by preheating your oven to 350°F (175°C). Prepare a baking sheet by lining it with parchment paper to prevent sticking.
In a medium mixing bowl, sift together the all-purpose flour, cocoa powder, baking powder, baking soda, and salt, ensuring everything is evenly blended.
In a large mixing bowl, use a hand mixer or whisk to beat together the granulated sugar, brown sugar, and eggs until the mixture is light, fluffy, and pale in color—this should take about 3 to 4 minutes.
Add the vanilla extract to the egg mixture, stirring gently until combined.
Slowly incorporate the dry ingredient mixture into the wet mixture, taking care to mix until just combined. Be cautious not to overmix, as the dough will be quite thick.
Gently fold in the roughly chopped pistachios and dark chocolate chips until they are well distributed throughout the dough.
With floured hands, shape the dough into a log approximately 12 inches long and 3 inches wide, placing it on the prepared baking sheet.
Bake in the preheated oven for 25-30 minutes, or until the log feels firm to the touch and a toothpick inserted in the center comes out clean.
After baking, remove the log from the oven and allow it to cool on the baking sheet for about 15 minutes.
Once it has cooled slightly, carefully slice the log diagonally into 1/2-inch thick slices using a serrated knife for clean edges.
Place the sliced biscotti back onto the baking sheet, laying them flat on one side. Return them to the oven and bake for an additional 10-15 minutes. After this, flip the biscotti to bake the other side for another 10-15 minutes, or until they are completely dry and crisp.
Allow the biscotti to cool completely on a wire rack before serving, enhancing their texture and flavor.
Notes
Arrange the biscotti artfully in a decorative tin or on an elegant serving platter. Serve with a side of hot espresso or coffee.