Step 1

Place the ginger, flour, rice flour and icing sugar in a food processor and process until combined. Add the butter and vanilla and pulse until the mixture resembles fine breadcrumbs. Add the egg yolk and process until mixture just comes together. Turn the dough onto a lightly floured surface. Gently knead until smooth. Divide dough into 2 even portions. Cover each portion in plastic wrap. Place in fridge for 30 mins to chill.

Step 2

Preheat oven to 180°C. Line 2 large baking trays with baking paper. Roll out 1 dough portion between 2 sheets of baking paper to a 3mm-thick disc. Use a 6cm round fluted pastry cutter to cut discs from the dough, rerolling the excess. Place on 1 lined tray. Repeat with the remaining dough portion. Place in the fridge for 10 mins to chill.

Step 3

Bake, swapping the trays halfway through cooking, for 12-15 mins or until the biscuits are light golden. Set aside on the trays to cool completely.

Step 4

Meanwhile, to make the lemon buttercream, use an electric mixer to beat the butter in a bowl until very pale. Add the icing sugar, in batches, beating well after each addition until smooth. Add the milk, lemon rind and lemon juice and beat until well combined. Place in a piping bag fitted with a 1cm plain nozzle. Pipe the buttercream over half the biscuits. Top with the remaining biscuits.

Step 5

To make the lemon drizzle, combine the icing sugar and lemon juice in a medium bowl. Place the mixture in a sealable plastic bag. Cut off 1 small corner. Pipe over each biscuit. Sprinkle with the lemon zest to serve.