2 tablespoons orange-flavored liqueur or vodka (optional)
3 large egg whites,
beaten until stiff
Combine sugar and water in a small saucepan and heat until sugar is melted and
mixture is clear. Remove and chill.
In a glass bowl, combine chilled sugar syrup, orange juice, lemon juice, zest
and liqueur. Mix thoroughly, then fold in the egg whites using an over-and-under
motion. Continue folding until no egg white streaks remain in the mixture.
mixture into an ice cream maker and freeze until firm, according to manufacturer's