Italian orange pistachio biscotti cookies are crunchy on the outside with a softer inside and practically melt in your mouth when they are dipped in your morning coffee!
Make the biscotti dough. In a stand mixer with a paddle attachment, cream the butter, sugar, orange zest, and vanilla extract together until it is light and fluffy. Add one egg at a time, making sure each egg is well incorporated before adding the next. In a separate bowl, combine the all purpose flour, baking powder, and salt. Whisk the mixture together until it is well combined. Gradually add the flour mixture to the egg mixture. Mix until it's combined, but do not over mix. Use a rubber spatula to stir in the pistachio nuts.
Shape the dough into logs. Preheat the oven to 325 degrees and line a baking sheet with parchment paper. Flour your work surface, then dump the dough out onto it and divide it in half. Flour your hands before shaping the dough. Divide the biscotti dough in half if you want smaller biscotti cookies, or you can shape it into one large log so it makes larger biscottis.
One log: Shape the biscotti dough into a 12-inch long, 4-inch wide log, then flatten the edges to the pan.
Two logs: Divide the biscotti dough in half. Shape the logs into 10 inches long, 3-4 inch wide logs.
Make the egg wash. Combine the egg white and water, then whisk until little bubbles form. Use a pastry brush to brush the egg wash onto the top of the biscotti logs. Sprinkle the tops with sugar.
First bake. Place the pan in the oven and bake the biscotti log for 30 minutes if you are making two logs, or 40 minutes if you are making one large log. Remove the pan from the oven and let it cool for 10 minutes. Cut the biscotti diagonally with a serrated knife so they are 1 1/2 inch thick. Place the biscottis on their sides back on the pan.
Second bake. Preheat to oven to 350 degrees. Place the biscottis back in the oven for 10-15 minutes, until they are golden brown on the edges. Remove from the oven and let them cool for 5 minutes. Mangia!