Boil the lemon juice, zest and stock syrup. Remove from the heat, add the milk and leave to infuse and cool. Once cooled, churn the mixture in an ice-cream or sorbet machine. It will take 20–25 minutes to churn to a creamy texture.
Five minutes before the sherbet is ready, whisk the egg whites to the soft peak stage and add to the sherbet while mixing. Continue to churn until ready. The