Preheat oven to 180 degrees celsius, or 350 farenheit.
Sift flour and baking powder together in a cast iron or casserole dish.
Add brown sugar and stir to combine.
In a separate bowl, whisk egg, milk and vanilla together.
Add to the dry ingredients and whisk until smooth.
Whisk melted butter into the batter.
In a Pyrex jug or similar, combine boiling water and golden syrup.
In a separate small bowl or cup, combine extra brown sugar and cornflour and mix thoroughly.
Sprinkle the sugar and cornflour mixture over the batter in the dish.
Gently pour the hot water syrup mixture over the top.
Bake uncovered for 45 minutes or until cooked and golden on top.
Serve with thickened cream or icecream.
