Preheat the oven to 180°C. In a saucepan, heat the castor sugar, unsalted butter and golden syrup. Add the cake flour and ground ginger. Lastly, add the lemon juice and allow the mix to cool. Roll into small balls and place on a Silpat mat. Bake until golden brown, and then transfer to an airtight container.
You could also store the raw mixture in the fridge and bake as needed.