1. Boil the water with grated lemon rind and sugar.
2. Blend the cornflour with the lemon juice.
3. Strain sugar solution on to blended cornflour.
4. Return to pan and boil for 6 to 8 minutes.
5. Whip the white of egg stiffly and fold into the mixture when it has cooled slightly.
6. Pour into wet moulds and turn out when set.
7. Serve with custard sauce.