Preheat oven to 180°C/356°F
Heat butter and milk until melted, add vanilla.
Sift dry ingredients into a bowl, make a well in the centre and add butter mixture.
Stir until smooth, pour into deep greased oven proof dish.
Mix brown sugar and cocoa together, sprinkle over mixture evenly.
Pour water over the top.
Bake for 40-45mins