Preheat oven to 350 F and place rack in center of oven.
Toast hazelnuts for 10 - 15 minutes or until the skins start to separate from the nut. Remove from oven and place in a clean tea towel to steam for about 5 minutes. Rub the hazelnuts in the towel to remove the skins. Let cool and then coarsely chop. Set aside.
Reduce oven temperature to 300F and line a baking sheet with parchment paper.
In a small bowl whisk together the eggs and vanilla extract. Set aside.
In the bowl of your electric mixer (or with a hand mixer) beat the flour, sugar, baking powder, salt, spices, and espresso powder until combined.
Gradually add the egg mixture and beat until a dough forms, add chopped nuts and chocolate chips about halfway through.
With floured hands divide the dough in half. On a lightly floured surface roll each half of dough into a log about 10 inches (25 cm) long and 2 inches (5 cm) wide.
Transfer logs to the prepared baking sheet, spacing about 3 inches (7.5 cm) apart, and bake for about 35-40 minutes, or until firm to the touch (logs will spread during baking, giving the characteristic biscotti shape).
Remove from oven and let cool on a wire rack for about 10 minutes.
On a cutting board, with a serrated knife, cut each log crosswise, into 3/4 inch (2 cm) slices. Be careful when moving these to the cutting board to ensure the logs don't break.
Arrange the slices on the baking sheet, cut side up, and bake 10 minutes. Turn slices over, and bake another 10 minutes or until firm to the touch.
Remove from oven and let cool. Store in an airtight container.