Preheat the oven to 180°C and line two trays with parchment.
Whisk butter and sugar until fluffy, then sift in flour, cornflour, spices, and salt.
Knead the mixture on a floured surface to form a soft dough.
Roll the dough between parchment paper to a 1cm thickness.
Prick with a fork and cut into dragon shapes using a cutter.
Bake on trays for 18–20 minutes until the edges are golden-brown.
Cool on trays briefly, then transfer to a wire rack to cool completely.
Mix icing sugar with boiling water to reach a thick, spreadable consistency.
Pipe an outline on each biscuit and fill with icing.
Set the icing before serving.