Bring sugar and water to the boil while stiring. Let it boil for 5-10 minutes to get a light sirup. Let it cool off. When cold, add champagne, lemon and heavy cream and stir well. Pour the mixture into an ice cream maker and let it run for 20-30 minutes.
Bring sugar and water slowly to the boil, and boil for 2-3 minutes. Let it cool off. Stir the finely-shopped peel and the lemon juice with the egg white and whip it to the sirup. Pour into ice cream maker and let it run for 30 minutes.