Preheat the oven to 175°C.
To make the Base, put the butter, golden syrup and brown sugar into a saucepan and stir over a low heat until melted.
Remove from the heat. Mix all the dry ingredients together in a bowl, then add to the saucepan.
Mix thoroughly. Press into a non-stick 20 x 30cm slice tin. Bake for 15 minutes.
Mark into squares while still warm.
Make the icing by putting all the ingredients together in a sauce-pan over a low heat.
Stir until melted, then beat until very smooth.
While the mixture is still hot, spread over the warm base.
When completely cold, cut through the icing and separate the squares.
Makes 24 squares.