Preheat your oven to 160 degrees and line two trays with baking paper.
Place the softened butter and caster sugar into the bowl of an electric mixer and mix on a medium speed for 5 - 7 minutes or until the mixture is light and creamy.
Reduce the speed of the mixer to slow, and gradually add the flour ½ a cup at a time. Mix for a further 30 seconds or until the mixture begins to resemble a dough.
Turn the mixture onto a lightly floured bench and gently bring it together to form a ball with your hands.
Cut the shortbread dough in half and wrap one piece in plastic wrap and pop it into the fridge until needed.
Roll the dough until it’s approximately 5mm thick and use an 8cm star shape cutter to shape the biscuits.
Transfer the shortbread to the prepared baking trays and bring together the remaining pieces of the dough, before repeating step 6 until you have used all of the shortbread dough - including the extra you have put aside in the fridge.
Bake the shortbread for 10 - 12 minutes or until the edges are just beginning to turn golden.Carefully remove the shortbread from the oven and allow it to cool on the baking trays for 15 minutes before transferring to a wire rack.