• 1⅓ cups sugar
• 1¼ teaspoons baking powder
• 1¼ teaspoons salt
• 1 teaspoon cinnamon
• 4 large eggs
• 2 teaspoons pure vanilla extract
• 3¼ cups all-purpose flour
• 1½ cups blanched hazelnuts, toasted
• 1¾ cups (10 ounces) semisweet chocolate chips
• 1 large egg white

Preheat the oven to 350 degrees F. Line a baking sheet with parchment paper.

In a small bowl, whisk together the sugar, baking powder, salt, and cinnamon.

In the bowl of an electric mixer fitted with the paddle attachment, beat the eggs and the sugar mixture together until the color is uniform and the mixture is thick. Add the vanilla and beat for 5 seconds. Add the flour in two batches and beat until just combined. Scrape down the bowl and mix for a few seconds more. Add the hazelnuts and chocolate chips and beat until just combined.

Turn the dough out onto the prepared baking sheet and shape it into a log about 16 inches long, 3½ inches wide, and ¾ inch thick. Use an offset spatula to smooth the surface of the dough. Bake for 20 to 25 minutes until firm, but not browned. Let cool on the pan for 10 minutes.

Lower the oven temperature to 325 degrees F.

While the log is cooling, whisk the egg white and 2 tablespoons water together and use a pastry brush to brush the egg wash onto the top of the log.

Cut the log into ¾-inch slices with a serrated knife, set them on the baking sheet cut sides up and down, and bake for 25 minutes. Remove the pan from the oven and cool on a wire rack for 5 minutes. Use a spatula to transfer the individual biscotti to a rack to cool completely. The biscotti will keep in an airtight container for up to 2 weeks.