Lime Ice Cream

Directions

1. 1
   Blend zest and 1/2 cup sugar in a food processor 30 seconds, then stir together with cream and milk in a heavy saucepan.
2. 2
   Bring to a boil over moderate heat, stirring occasionally, and remove from heat.
3. 3
   Steep, covered, 30 minutes.
4. 4
   Bring remaining 1/2 cup sugar and 1/4 cup plus 2 tablespoons lime juice to a boil in a 2-quart heavy saucepan, stirring until sugar is dissolved, then boil, swirling pan occasionally, until syrup just begins to turn very pale golden.
5. 5
   Remove from heat and whisk in steeped cream.
6. 6
   Whisk yolks with salt in a large bowl and add cream mixture in a slow stream, whisking.
7. 7
   Return to saucepan and cook over moderately low heat, stirring constantly with a wooden spoon, until custard coats back of spoon and thermometer registers 170F (do not let boil).
8. 8
   Pour through a very fine sieve into a clean bowl and cool, stirring occasionally.
9. 9
   Stir in remaining 1/4 cup lime juice and chill custard, covered, until cold, at least 3 hours.
10. 10
    Freeze custard in ice cream maker.
11. 11
    Transfer ice cream to an airtight container and put in freezer to harden.