Grate the rind off 1 lemon and press the juice out
of all four. Bring one cup of water to the boil, dissolve the sugar
and simmer for 5 minutes. Allow the syrup to cool down, and stir in
the lemon juice and rind and the egg whites. Freeze the mixture 4 hours,
break it into chunks and then blend shortly in a food processor.
Mix the egg yolks and
the sugar and beat the mixture 5 minutes with an electric mixer. Add
the cream and heat the mixture, either au bain marie or in the micro
wave, first 30 seconds and then 15 seconds every time. Keep mixing.
When the mixture thickens and is hot, take it out and allow it to cool
down completely. Stir in the chocolate and mint and freeze for 5 hours,
stir every hour, or use an ice cream maker.