Recipe by by Jennifer McLaughlin
Preheat the oven to 190C/gas 5. Grease a flat baking tray, then line with a sheet of baking paper.
Beat the butter, then cream it with the icing sugar and all the zests until light and fluffy. Fold in the flour and baking powder, then use your hands to form a dough – do not overmix.
For rectangular shortbread, roll out to about 1cm thick and cut into fingers. For round biscuits, roll into 20 even-sized balls. Prick the surface of each. Reroll any scraps and repeat.
Put your shortbread onto the tray, then chill in the fridge for 10–15 minutes, before baking in the ovenfor 12–15 minutes until pale and crisp.
Remove from the oven and allow to cool for 5 minutes, then transfer to a cooling rack and sprinkle with sugar. This shortbread will keep for up to a week in an airtight container.