Directions

1. COOK 1 cup milk in a heavy saucepan over low heat until bubbly. Stir in 1 cup basil leaves, and remove from heat. Cover and let stand at room temperature 20 minutes.
2. PROCESS basil mixture in a blender until smooth, stopping to scrape down sides. Pour mixture through a wire-mesh strainer into a bowl, discarding solids. Set aside.
3. COOK remaining 1 cup milk, whipping cream, and 1/2 cup sugar in saucepan over medium heat, stirring often, just until mixture is bubbly. Remove from heat.
4. BEAT egg yolks and remaining 1/2 cup sugar at medium speed with an electric mixer until thick and pale. Gradually stir about one-fourth of hot milk mixture into yolks; add to remaining hot mixture, stirring constantly. Stir in basil mixture and, if desired, liqueur; cook over medium heat, stirring constantly, 6 minutes or until mixture thickens and coats a spoon. Cover and chill 4 hours.
5. POUR chilled mixture into freezer container of a 1-gallon electric ice-cream freezer, and freeze according to manufacturer's instructions.
6. Pack with additional ice and rock salt, and let stand 1 hour. Serve in frozen lemon shells, and garnish, if desired.