Preheat oven to 190 degrees celsius. Grease and line a 20x30cm baking tray with baking paper and set aside.
Cream butter and sugar together until pale and fluffy.
Add the sifted plain flour, baking powder and ginger and mix to combine.
Knead the dough on a floured board until it comes together (it will be quite dry and crumbly).
Press the dough into the prepared tin and smooth the top with a spoon.
Bake for 20-25 minutes or until lightly golden.
To make the icing, place the butter, sifted icing sugar, golden syrup and ginger into a saucepan over medium heat and stir until the butter has melted.
Pour the icing over the still warm slice.
When the icing has just set, cut into slices.
Store in an airtight container.