Preparation In a large bowl with an electric mixer beat yolks until thick and pale. In a very small saucepan heat sugar and water over moderately high heat, stirring, until a thermometer registers 215°F. Remove pan from heat. With mixer on low speed, add sugar mixture to yolks in a slow stream. Increase speed to high and beat mixture until thick and ribbonlike. Whisk in buttermilk. Freeze custard in an ice-cream maker. Transfer sherbet to an airtight container and put in freezer to harden. Buttermilk sherbet may be kept 1 week.
Preparation In a large bowl with an electric mixer beat yolks until thick and pale. In a very small saucepan heat sugar and water over moderately high heat, stirring, until a thermometer registers 215°F. Remove pan from heat. With mixer on low speed, add sugar mixture to yolks in a slow stream. Increase speed to high and beat mixture until thick and ribbonlike. Whisk in buttermilk. Freeze custard in an ice-cream maker. Transfer sherbet to an airtight container and put in freezer to harden. Buttermilk sherbet may be kept 1 week.