Heat the oven to 180 C / 350 F. You will need a 23-25 cm casserole dish or bowl at least 5-6 cm deep. ( see my picture) 10 in x 2- 3 inches deep
Put the brown sugar, custard and water into a pot and set aside
Put the flour, baking powder, cocoa and sugar into a bowl and stir well to combine.
Whisk the milk and egg together then stir in the warm butter and pour into the bowl with the dry ingredients and mix till a nice batter is formed. Pour inro the casserole dish and press the raspberries into the batter at even intervals all over the pudding.
Sprinkle the top of the batter with the extra cocoa powder
Heat the custard mixture till just under boiling point stirring to stop it sticking,
Pour this hot mixture over the batter and then put into the oven.
Bake for 25 minutes, then take out and stand for 5-10 minutes.
Serve with ice cream or more custard and cream