MIxthe egg, water, oil and brownie mix together until well blended (mixture may be lumpy).
Spreadthe mixture evenly into the lightly-greased rectangular tin. Top with all the chopped pieces of chocolate bars, pressing them gently into the mixture.
Bakein the centre of the oven for around 20-25 minutes or crisp and risen on top. Allow to cool on a wire rack then slice into bars.
TipsYou can top with any chocolate bars you desire! Keep a watch on the brownie as it bakes and if it looks like any of the pieces are catching you can always cover the brownie with foil to prevent it catching any further.