Biscotti is an Italian almond biscuit that originated in the city of Prato. They are twice-baked, oblong-shaped, crunchy biscuits that are usually dipped in a drink to eat. Store biscotti in an airtight container for up to 2 weeks.
Preheat oven to 180 degrees C. Line two baking trays with baking paper.
Using electric beaters, beat the sugar, egg and yolk in a mixing bowl for 3-4 minutes or until thick and creamy. Gently fold in the sifted flour and baking powder until just combined. Fold in the nuts.
Shape the mixture on a lightly floured surface into a 24cm-long log. Place the log on a prepared tray and flatten slightly to 2cm thickness. Bake for 20 minutes or until firm. Cool.
Reduce oven temperature to 140 degrees C. Using a serrated knife, cut the log into 5mm-thick slices. Spread out in a single layer on trays.
Bake for 20 minutes, turning once halfway through cooking time, or until crisp. Remove to wire racks to cool.