Preheat the oven to 350 degrees F. Line a baking sheet with parchment paper.
In the bowl of a stand mixer fitted with the paddle attachment, combine the sugar, baking powder, salt, and cinnamon. Add the eggs and beat until the color is uniform and the mixture is thick. Add the vanilla and beat until combined, about 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 into a log about 16 inches long, 3 ½ inches wide, and ¾ inch thick. 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.
Using a serrated knife, cut the log into ¾-inch slices and set them on the baking sheet cut sides up. Bake for 25 minutes. Remove the pan from the oven and cool on a wire rack for 5 minutes. Transfer the individual biscotti to a rack to cool completely. The biscotti will keep in an airtight container for up to 2 weeks.