Preheat oven to 170C, fan 150C, gas 5.
Lightly grease 6 holes of a muffin tin. Sieve the cocoa into a large bowl with the flour and bicarbonate of soda. Stir in the WHITWORTHS LIGHT SOFT BROWN SUGAR and make a well in the centre.
Beat the milk, egg and oil together in a jug, pour into the well and stir quickly to make a batter. Spoon into the muffin tin and bake for 15 mins or until risen and firm to the touch.
Heat the custard according to instructions on pack, tip in the chopped chocolate and stir until melted and smooth.
To serve, turn the puddings into bowls and pour over the custard.