This produces and ice cream with a vibrant green color and a fairly assertive basil flavor.
This recipe is from the October 2004 issue of Gourmet, via Epicurious.
2 cups whole milk
3 tablespoons chopped fresh basil
1/2 cup sugar
4 large egg yolks
1/2 cup well-chilled heavy cream
Bring milk, basil, 1/4 cup sugar, and a pinch of salt to a boil in a 2-quart heavy saucepan, stirring, then remove from heat and let steep 30 minutes. Transfer to a blender (reserve saucepan) and blend until basil is finely ground, about 1 minute.
Beat together yolks and remaining 1/4 cup sugar in a medium bowl with an electric mixer until thick and pale, about 1 minute. Add milk mixture in a stream, beating until combined well. Pour mixture into reserved saucepan and cook over moderate heat, stirring constantly with a wooden spoon, until mixture coats back of spoon and registers 175°F on thermometer (do not let boil). Immediately remove from heat and pour through a fine-mesh sieve into a metal bowl. Set bowl in a larger bowl of ice water and stir until cold, 10 to 15 minutes.
Stir in cream and freeze in ice cream maker. Transfer ice cream to an airtight container and put in freezer to harden, at least 2 hours.