1.Have butter for shortbread and butter cream frosting at room temperature.
2.Beat butter, extract and sifted icing sugar in small bowl with electric mixer until light and fluffy, beat in rum and brandy. Add sifted flour, cornflour and nutmeg, beat on low speed until just combined. Enclose dough in plastic wrap, refrigerate 10 minutes.
3.Shape dough into two 30cm (12-inch) logs, roll logs on baking paper until smooth, refrigerate 1 hour.
4.Meanwhile, preheat oven to 160°C (140°C fan forced). Line oven trays with baking paper.
5.Cut each log into 50 slices. Place slices, about 2.5cm (1 inch) apart, on trays. Bake shortbreads about 12 minutes. Stand on trays 3 minutes before transferring to wire racks to cool.
6.Make butter cream frosting. Beat butter in small bowl with electric mixer until as white as possible. Gradually beat in extract and half the sifted icing sugar. Beat in brandy and rum, then remaining icing sugar.
7.Spoon frosting into piping bag fitted with small fluted tube, pipe frosting onto shortbread. Dust with combined sifted extra icing sugar and extra nutmeg.
This recipe makes a lot of little one-bite shortbreads. If you like, make 50 shortbreads and freeze the remaining log, wrapped in baking paper then plastic wrap, for up to 3 months. Thaw in the fridge overnight before slicing and baking. You will need to halve the butter cream frosting if only baking 50 shortbreads.