Preheat the oven to 350°F. Using a stand or hand mixer, whip the eggs with sugar until the mixture doubles in volume.
In a separate bowl, combine flour, baking powder, and cacao.
Add the egg mixture into the flour mixture and stir to combine. Mix in the chopped hazelnuts and chocolate chips.
Divide the dough in half. Form two or four logs on a baking sheet lined with parchment paper. Note: The dough may be sticky. To better handle it, wet your hands with cool water.
Bake for 35 minutes. Remove the dough from the oven and set it aside to cool for 10 minutes. Reduce oven heat to 275°F.
Cut logs diagonally into 3/4-inch thick slices. Place the slices on their sides on a parchment paper covered baking sheet. Bake for 8 to 10 more minutes.
Create a water bath by bringing a saucepan of full of water to boil. Place a metal bowl on top of the saucepan. Pour the chocolate chips into the bowl, stirring continuously until fully melted. Remove the bowl from the saucepan and dip half of each biscotti in the melted chocolate.
Lay dipped biscotti on a parchment paper lined baking sheet until the chocolate hardens.
Serve with a hot cup of coffee or tea! Serve leftovers in an airtight container on the counter or freeze for future snacking.