Heat the Oven - Set the oven rack to the middle position. Heat to 325ºF (163ºC). Line a sheet pan with parchment paper.

Toast the Almonds - Spread the almonds on a sheet pan. Toast for 10 minutes, stirring halfway through.

Chop the Almonds - Use a chef’s knife to coarsely chop the almonds. Aim for medium pieces so they distribute evenly but still have a characteristic almond appearance.

Mix Dry Ingredients - In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

Mix the Wet Ingredients - Add 2 eggs to the bowl of a stand mixer fitted with the whisk attachment. Beat on medium-high speed (setting 8) until the eggs turn pale yellow and nearly double in volume, about 3 minutes. Reduce to medium speed (setting 5) and slowly pour in the sugar, mix until fully incorporated, about 15 seconds. Add the melted butter, almond extract, and vanilla, and mix again until smooth and combined, about 15 seconds. The mixture should be thick yet pourable.

Make the Dough - Add half of the flour mixture to the egg mixture, and gently stir with a spatula until just combined. Add the remaining flour and the chopped almonds, stirring until the dough just comes together; it will be slightly tacky. Avoid over mixing to maintain a crisp, tender biscotti.

Portion the Dough - Divide the dough into two equal portions and place them on the sheet pan. With lightly floured hands, shape each portion into an 8-by-3-inch rectangle. Space the loaves at least 4 inches apart. Smooth the edges to create a slight dome. Brush the tops with the egg white wash. If desired, lightly sprinkle granulated sugar on top.

Bake - Bake for 25 to 30 minutes, or until the loaves are lightly golden, rotating the pan halfway through. Let them cool on the baking sheet for 30 minutes.

Slice the Biscotti and Bake Again - Place the loaves on a cutting board. Use a serrated knife to make a ¾ inch thick slice, cut on a slight bias. Place the slices cut side down on a wire rack set in the baking sheet. Bake for 15 minutes, then flip them over. Continue baking until lightly golden brown and crisp, about 10 to 15 minutes.

To Serve - Cool the biscotti on the wire rack, then serve when dry and crisp.