Place the flour, hazelnuts, sugar, baking powder, salt and orange zest directly in the bowl of a stand mixer and stir to combine.
Add in the cubed butter and mix together till you get a sandy texture.
Mix in the beaten eggs and extracts until well combined and you have a soft workable dough.
Divide the dough into 2 equal pieces.
Work with one piece at a time while keeping the other covered.
Place one piece of dough between 2 sheets of parchment paper.
Using a rolling pin, roll out the dough to approximately 12 inches long and 6 inches wide. And, approximately 1/4 inch thick.
Remove the top parchment paper while keeping the bottom one in place.
Spread half of the Nutella over the dough till about a 1/2 inch from the edge.
Gently start rolling the log from the longest width with the help of the wax paper underneath it by lifting the paper up and easing the dough over the Nutella.
Continue rolling by hanging on to the wax paper as you roll.
Seal the edges by pinching the dough together and tucking them underneath.
With the help of the wax paper, lift and transfer the log onto the prepared baking sheet, seam side down.
Repeat with the remaining piece of dough.
Make sure to leave enough room between the 2 logs because they will spread out somewhat.
Brush the tops of the logs with the beaten egg whites.
Sprinkle the tops of the biscotti logs with the sugar granules.
Bake in a preheated oven at 350 degrees F., for approximately 35 minutes.
When ready the biscotti logs will have a deep golden brown colour and will feel firm to the touch.
Allow the biscotti logs to cool for about 20 to 30 minutes before slicing into 1 inch slices.
Cool completely before storing in an air tight container.