Preheat oven to 180 degrees celsius (fan-forced). Line an 18X28cm rectangular slice tin with baking paper and set aside.
To make the base, sift the plain flour into a bowl. Add the brown sugar and coconut and stir to combine.
Add the melted butter and mix well until crumbly and completely combined.
Press the mixture firmly into the base of the prepared tin and smooth with a spoon.
Bake for 15 minutes or until lightly golden.
To make the filing, place the golden syrup, condensed milk and butter into a small saucepan over low heat.
Stir continuously for 10 minutes or until the caramel has thickened (make sure your heat is very low and you continue stirring until the sauce has obviously thickened).
Pour the caramel over the cooked base and return to the oven for a further 15-20 minutes or until golden.
Remove from the oven and set aside until cool.
Melt the white chocolate and vegetable oil in the microwave on 50% power for 3-4 minutes, stirring every 30 seconds with a dry metal spoon.
Pour the chocolate topping over the caramel layer.
Cut into slices just before the chocolate topping sets completely.
Store in an airtight container.