Preheat the oven to 350°F. Line a baking sheet with parchment paper.
In a large bowl, combine the flour, baking powder and almonds.
In a separate bowl, whisk together the eggs, sugar, butter, vanilla, almond extract and orange zest. Stir the wet ingredients into the flour mixture until a soft, sticky dough forms.
Transfer the dough to a lightly floured work surface. Sprinkle more flour on top if the dough is sticky. With clean hands, form the dough into a smooth ball. Divide the dough in half, and then roll each into 12-inch logs. Transfer to the prepared baking sheet. Pat down each log so that it is about 2-inches wide. Brush the tops of the logs with the beaten egg white.
Bake for 15 to 20 minutes. Remove from the oven and let cool in the pan on a rack for 5 minutes. Gently transfer each log to a cutting board. Cut diagonally into ¾-inch slices.
Return the biscotti to the baking sheet and bake for an additional 10 to 15 minutes until golden brown. Take the pan out of the oven and turn each cookie to the other side. Bake an additional 5 to 10 minutes until crisp. Let the biscotti cool on a rack.