Preheat the oven to 170°C fan bake. Line a baking tray with baking paper.
Cream the softened butter and sugar together until light and fluffy.
Add the plain flour, baking powder and ground ginger. Mix until combined.
Spread the mixture evenly over the prepared tray and press down firmly.
Bake for 25–30 minutes, or until golden.
While the base is baking, prepare the icing. Melt the butter and golden syrup together in a saucepan over low heat.
Stir in the ground ginger.
Gradually add the icing sugar, mixing until the icing is smooth and well combined.
Spread the ginger icing over the base immediately after removing it from the oven.
Allow the slice to cool completely and the icing to set before cutting into squares or bars.