Combine first 5 ingredients in a large bowl; beat with a mixer at medium speed until well blended. Stir in chocolate.
Pour mixture into freezer can of a 2-quart hand-turned or electric freezer. Freeze according to manufacturer's instructions. Pack freezer with additional ice and rock salt, and let stand at least 1 hour before serving.
Tip: Egg substitute is pasteurized to kill any harmful bacteria. It can safely be used in recipes that traditionally call for raw eggs, such as no-cook ice creams.