Grate the rind of three lemons and put it into the mixing bowl with the castor sugar. Separate yolks from whites if the eggs and add the yolks to the lemon rind and sugar with the cornflour and enough of the measured milk to make a smooth creamy consistency. Beat these ingredients well. Heat the remaining milk and pir it gradually on to the lemon mixture stirring all the time. Return the mixture to the pan and stir over a gentle heat until it comes to a boil. Simmer for a few minute and set aside to cool.
Squeeze the juice of three limes. Add enough juice to make 200 ml. Melt gelatine in the lemon juice in a small pan by heating it and when cool, stir into the lemon mixture. Stir in double cream, beat egg whites till stiff and lightly fold into the mixture. Immediately turn the souffle mixture into prepared dish. It should come at least 1" above the top of the dish and be held in by the paper collar. Leave the souffle to set for a few hours in the refrigerator.