Peel the zest of the lemon and lime and finely julienne. Add the zest to the sugar with split and scraped vanilla bean.
Place the sugar, vanilla and zest into the bowl of a stand mixer fitted with a whist attachment, add two whole eggs and a pinch of salt. Whisk on high speed for 5 minutes until the mixture is pale, light and fluffy.
Remove the bowl from the mixer and tip in nuts, flour and baking powder. Fold the flour and nuts through with a spatula until you have a firm dough.
Remove the dough from the mixer and knead on a lightly floured bench to ensure all the flour has been mixed through the dough.
Split the dough into two (2) pieces and roll the dough into two (2) long sausages approx 25cm long and 5cm wide. Place the dough onto a baking tray lined with baking paper and rest the dough for 5 minutes.
Once the dough has rested place it in a pre-heated oven combi setting 170 °C for 25 minutes. Once baked remove the dough from the oven and place it on a cooling rack to cool for 20 minutes
Once cool finely slice the dough into 1/2 cm diagonal pieces. Place each piece onto baking trays lined with baking paper and place into a pre-heated oven combi setting 140 °C for 15-20 minutes turning each biscotti over once. Cook until the biscotti are completely dried out.
Once baked cool again on a cake rack and serve with espresso coffee.