method
1. Rub the sugar on the lemon zest.
2. Squeeze and strain the juice from the lemon, and make up to 250 ml with water.
3. Put the liquid in a heatproof container, sprinkle on the gelatine and leave to soften.
4. Stand the container in a pan of hot water and stir until dissolved.
5. Separate the egg.
6. Beat the yolk and stir it into the gelatine mixture.
7. Crush and add the sugar.
8. Simmer the mixture for 3 minutes over low heat, stirring all the time.
9. Remove from the heat and leave to cool.
10. Whisk the egg white until stiff and fold it into the mixture.
11. Pour into individual glasses and leave for about 1 hour to set.
