Mix first 4 ingredients in mixing bowl. press into tray, bake for 10 mins in oven.
Mix condensed milk, golden syrup and extra butter in a saucepan over medium heat, stirring constantly, till it slighty starts to thicken and changes a slightly darker colour. Should only take about 10 minutes or so.
Spread caramel mix over base and bake for a further 10 minutes. Cool.
Spread top of caramel with melted white chocolate and refridgerate til set.