Preheat oven to 350°F/180°C, conventional setting (that's no steam, those of you who are regulars here!). Line a baking sheet with parchment paper and set aside.
Put flour, baking soda, baking powder, salt, powdered ginger, and cocoa powder into a large bowl. Whisk to combine thoroughly and break up any lumps.
1 ¾ cups all-purpose flour, 1/2 tsp baking soda, 1/2 tsp baking powder, 1/2 tsp flaky salt, 1 ½ tsp ground ginger, 3 Tbsp Dutch process cocoa
Add the chocolate chips, raisins and 1 ¼ cups pecans, and mix with a spatula or spoon to coat all the inclusions with flour.
1 cup semi sweet chocolate chips, 1 cup raisins, 2 cups pecan halves
Put the remaining pecans and the granulated sugar into the bowl of a food processor. Process until the nuts are finely ground.
2 cups pecan halves, 1/2 cup granulated sugar
Put the pecan sugar mixture into another bowl, then add the brown sugar, melted butter, vanilla, whole eggs, and the egg yolk from the separated egg. Whisk together until smooth then scrape into the large bowl containing the dry ingredients. Stir together until it forms a mass and there are no visible streaks of flour left.
1/2 cup dark brown sugar, 2 Tbsp unsalted butter, 1 tsp vanilla paste or extract, 2 large eggs, 1 large egg
Turn the dough out onto a well-floured surface. Knead it together a couple of times to make sure it's evenly mixed, then use a dough scraper or knife to cut the dough into two. Flour your hands and roll each piece into a thick log, about 10 inches (25cm) long and 2 inches (5cm) in diameter. Carefully transfer the logs to the lined baking sheet, leaving a couple of inches between them as they'll expand during baking. Whisk the leftover egg white and brush the tops of the logs, then sprinkle generously with extra sugar.
1 large egg, 3 Tbsp granulated sugar
Bake the biscotti logs until the center feels firm when you press it gently, about 40-45 minutes. Let the logs cool on the baking sheet just until cool enough to handle, about 15 minutes.
Reduce oven temperature to 325°F/165°C. Using a sharp bread knife, slice the biscotti about 3/8 inch (1cm) thick, on a slight angle, and lay them on the baking sheet, close together. You'll likely need a second lined sheet, or you can do this step in batches. Return baking sheet to the oven to toast and dry out the biscotti, about 9 minutes per side. Cool completely before packing them into an airtight container. Biscotti will stay fresh for about 2-3 weeks and can be frozen, well wrapped, for up to 6 months.