Jo baked her way into our hearts by winning The Great British Bake Off in 2011. Her cookbooks, Home Baking and A Passion for Baking, are full of easy cakes and impressive desserts to share with friends and family.
1Grind the lavender sugar with the extra lavender pieces using a pestle and mortar.
2Tip the ground sugar into the bowl of a food processor and beat with the butter until pale, light and very fluffy. Mix in the vanilla extract. Sift in the flour and cornflour, and mix until smooth and thoroughly combined.
3Spoon the dough into a piping bag fitted with a 1cm star nozzle and pipe 30 x 4cm stars on to a baking tray lined with baking paper. Chill in the fridge for at least 45 minutes.
4Preheat the oven to 180°C, fan 160°C, gas 4. Bake on the middle shelf of the preheated oven for 14-16 minutes until pale golden. Cool on the baking sheets for 5 minutes, then transfer the shortbreads to a wire rack to cool.
5Whisk the icing sugar and butter together until pale and creamy. Mix in the orange zest and juice, then spoon into a piping bag and pipe on to half of the biscuits. Sandwich together and dust with icing sugar.
For St Clements (orange and lemon) shortbreads, use caster sugar and add the finely grated zest of 1 lemon.