Preheat oven to 180°C/350°F/Gas Mark 4. Line two to three baking trays with baking paper. Cream butter and sugar, then beat in egg and brandy. Combine nuts with sifted flour, baking powder and cardamom. Add half nut mixture to butter, mix well. Add remaining nut mixture and gently bring together – don’t overwork. Knead lightly on a bench for 10 seconds. Divide into six, roll each piece into a 10 cm (4 in) long log and cut each log into ten. Take one piece at a time in your hands, roll into a cylinder with pointed ends, bend into a crescent and place on a paper-lined baking tray. (As you work keep remaining mixture covered with plastic to prevent it from drying out.) Bake until golden, 15–20 minutes. Remove to a wire rack.
Immediately brush the tops of the hot shortbread with combined rosewater and water. Leave for a minute then dust liberally on both sides with sifted icing sugar. Leave to cool completely. Store in an airtight tin for up to 2 weeks.