Preheat oven to 160 degrees celsius fan-forced (180 degrees celsius conventional). Grease a large 6 cup capacity (1.6 litre) baking dish and set aside.
Place the brown sugar, self raising flour, melted butter, egg, milk and golden syrup into the Thermomix bowl and mix together on Speed 5, 20 seconds or until well combined.
Pour into the prepared dish.
In a clean Thermomix bowl, mix the brown sugar and cornflour together on Speed 6, 10 seconds.
Sprinkle over the pudding base. Carefully pour the boiling water over the top.
Bake in the oven for 40 minutes or until the top is golden and firm to the touch.
Serve with ice-cream or custard.