Preheat the oven to 300F. Place the almonds on a rimmed baking sheet and toast for about 3 minutes. Remove and set aside.
Increase the oven temperature to 350F.
In a small bowl whisk together the flour, baking powder, and salt. Set aside.
In a large bowl, stir together sugar, butter, vanilla, and almond extract. Add eggs and mix to combine. Add the flour mixture 1/3 at a time to the butter/egg mixture and stir until just combined. Stir in the almonds.
Dampen your hands and shape dough into 2 4"x10" logs on a parchment-lined baking sheet. Beat the egg with the teaspoon of water. Brush on the egg wash.
Bake about 30-35 minutes until lightly golden. Transfer the baking pan to a wire rack and cool for 10-15 minutes, cool enough to handle.
Using a very sharp, serrated knife, cut logs into 3/4 inch slices and arrange on the baking sheet, cut side down. Bake biscotti again for 15 minutes. Remove from the oven and turn each piece over to the other cut side and bake another 10-15 minutes until golden and dry.
Transfer to a wire rack to cool completely.