Alcohol acts like anti-freeze in ice cream, you can find discussions on-line of various ratios of alcohol, sugar and salt needed to get it to freeze but not become rock hard.

Thanks to Karla for doing all the experimenting for us! Sounds yummy..I may finally beak down and buy a machine. For the past two years, I made instant gratification ice cream by putting frozen berries in a food processor and adding heavy cream until it was smooth like soft custard ice cream. A touch of DaVinci Raspberry SF if needed.