Beat the eggs and sugar until liquid then stir in the milk and strain into
a bowl over a pan of simmering water. Stir over a gentle heat for 20
minutes until the custard is as thick as single (light) cream. Pour into a
clean bowl, cover and leave to cool. Whip the cream until very thick but
not too stiff, then mix it lightly with the egg custard and vanilla
essence. Turn into a freezer container and freeze for 1 hour. Turn out
into a chilled bowl and beat until smooth. Return it to the container and
freeze until firm.