Preheat the oven to 180°C (350°F) and grease a 20cm baking round baking dish.
Melt the butter, milk, vanilla extract and golden syrup in a saucepan on a low heat until the butter melts.
In a bowl mix the sugar, brown sugar and self raising flour together.
Pour over the wet ingredients and mix all together until just combined.
Chop 90g of the Caramilk chocolate into small pieces and fold through the batter.
Pour into the prepared dish.
Chop the remaining Caramilk chocolate into very small pieces and place in a separate bowl.
To that, add in the brown sugar and condensed milk and then the boiling water.
Stir together.
Pour the mixture over the cake batter.
Place in the oven for 30-35 minutes. The top will be set and golden but underneath will still be bubbly and liquid.
Video
Notes
* If you can't get your hands on Caramilk chocolate, you can replace with Caramac or any other caramelized white chocolate. Or make this a white chocolate self saucing pudding.