Combine the flours, caster sugar and baking powder in a bowl and mix well. Add three eggs and mix well until all the flour is absorbed into the dough. Add the remaining ingredients and mix, distributing them well.
Divide the dough in half. Take the first half, knead lightly and roll into a baton. Place it on a baking tray lined with baking parchment.
Repeat the procedure for the second half and place at least three inches apart from the other baton on the baking tray.
Bake in the preheated oven for between 20 to 25 minutes or until slightly soft but firm to the touch. Remove from oven and slice into 1 inch thick slices. Return them to the baking tray.
Bake for about 7 to 10 minutes further at the same temperature, until biscotti are firm. Depending on how your oven works, biscotti may require turning half way through to make sure they dry out evenly.