Biscotti al Limone

Directions

• Put the butter, sugar and salt in the bowl of a stand mixer with the paddle attachment and cream the mixture at high speed until pale and fluffy; it will take about 3–4 minutes. Add the egg, vanilla and lemon zest and mix again at high speed until the egg is fully incorporated, scraping down the sides of the bowl with a silicone spatula, if necessary.
• Sift, in this order: the bicarbonate of soda, flour and cornflour into the bowl, then squeeze 1 ¾ oz (50g) of juice from the zested lemons and add it to the bowl. Mix at low speed until all the ingredients are well combined in a smooth dough. If you add the lemon juice directly to the buttery mix, the mixture might curdle, but keep going and it will come together nicely when adding the flours. The dough will be rather sticky but wrap in cling film and chill it in the fridge for at least 1 hour and it will become much stiffer and more manageable.
• When ready to bake, set the shelf in the middle of the oven and preheat it to 350°F/160°C/Gas mark 4. Line two baking sheets with baking paper or silicone mats. Put the icing sugar on a plate. Take small lumps of dough, roughly a tablespoonful or about 3/4 oz (20g), roll them between your hands to shape them as little balls. Roll them very generously in the icing sugar until they are fully coated in a thick layer of sugar, and distribute them across the baking trays, spacing them at least 2 in (5 cm) apart.
• Bake one sheet at a time for 12–13 minutes, or until golden cracks appear on the sugared surface of the biscuits. The biscuits are done when the bottoms look golden. Slide the baking paper onto a wire rack and allow the biscuits to cool completely before taking them off the paper. Serve at room temperature. Biscotti al limone keep for up to a week in an airtight container.