Preheat the oven to 180C/350F/Gas 4. Line 2 baking trays with parchment paper or a silicone mat, and set aside.
Whisk together the flour, baking powder, and salt. Set aside.
In a separate large bowl, whisk together the butter and sugar until combined. Add the eggs and vanilla, and mix until smooth and combined.
Add the dry ingredients and mix until combined.
Divide the dough in half and transfer to the prepared baking trays. Shape each half into a log about 18cm (7") long, 9cm (3 1/2") wide, and 2cm (3/4") thick.
Bake for 25 - 30 minutes or until golden brown. Allow to cool on the baking tray for 20 minutes, or until cool enough to handle.
Lower the oven temperature to 140C/275F/Gas 1.
Use a sharp serrated knife to cut the log into 2cm (3/4") thick slices. Place the slices, cut sides down, on the lined baking tray.
Bake for 40 minutes, turning them over halfway through.
Allow to cool on the baking tray for 5 minutes before transferring them to a wire rack to cool completely.
Video
Notes
Biscotti stays fresh, kept in an airtight container, at room temperature for up to 1 - 2 weeks. They also freeze well for up to 3 months. Thaw at room temperature.The dough also freezes well for up to 3 months. Thaw overnight in the fridge, and allow to come to room temperature before shaping.