In a mixing bowl combine the butter and sugar and beat, with a whisk or hand mixer, until light and fluffy, scraping down the sides periodically. Add the orange zest and beat in the eggs 1 at a time. Stir in the vanilla.
Gently mix in the baking powder, salt and flour. Once the flour is incorporated fold in the almonds, raisins and anise.
Divide the dough into 2 pieces. If the dough is sticky dust your hands with a little flour. Roll the dough into 2 logs the length of the sheet tray. Beat the egg white with 1 tablespoon of water in a small bowl. Brush the dough logs with the egg white and sprinkle with turbinado sugar. Bake in the preheated oven for about 30 minutes.
Remove from the oven to a cutting board and slice on the bias with a serrated knife while they are still warm. Slicing while warm will prevent crumbling.
Lay the biscotti back on the sheet tray(s), cut sides down, and return to the oven for another 10 minutes. This will harden the biscotti but not make them like rocks.
Remove from the oven to a serving platter and serve with coffee or Vin Santo for dipping.