1. Preheat oven to 180°C (350°F). Line a baking sheet with baking parchment and set aside. Mix the flour with the sugars, baking powder and salt in a large bowl. Chop the chocolate and add it together with the pistachios to the bowl and mix. Set aside.

2. In a small bowl mix the eggs with the melted (and cooled) butter, vanilla extract, and cocoa powder until well combined. Pour the mixture into the large bowl and mix all until well combined – the dough will be quite tough, so feel free to use your hands. Divide the dough into two equal pieces and roll each piece into a log with a length of about 25cm. Sprinkle sugar onto your work surface and roll the logs in the sugar so they are covered completely. Place on the baking sheet and bake for about 18-20 minutes. Take out of the oven and let cool down on the baking sheet for about 30 minutes.

3. Reduce the temperature of the oven to 150°C (300°F). Cut the logs into 1,3cm thick slices and place again on the baking sheet and bake for another 15-20 minutes until dry. Take out of the oven and let cool down completely on a wire rack. Store in an airtight container.