Adapted from Desserts 1-2-3 by Rozanne Gold, this sorbet (or ice cream, or whatever) and variations are big hits with friends and family. Super simple, but not so's anyone would notice. It started with just lemons, sugar, buttermilk, and salt, but I couldn't resist tarting it up over the years, with pomegranate, lime, blood-orange, and other variations. This is one of the most successful, with a delicate green color and a smooth, tart, perfumed goodness. —EdibleAuk
Cut zest (no white pith) from lemons and oranges, then halve and juice them all. You should have more combined juice than you need; measure 1/2 a cup and reserve the rest for another cocktail. I mean, use.
In a food processor, combine sugar, all the zest, and the basil leaves. Process until zest and leaves have disappeared entirely, becoming a mere color to the sugar.
In a large bowl, combine doctored sugar and 1/2 cup mixed juice. Stir well. Add the buttermilk and salt, and stir until the sugar has dissolved.
Refrigerate mixture (covered) for at least 4 hours. Chill in your ice-cream freezer until firm. Sometimes this benefits from being transferred to a covered container and frozen for a further hour before service. Garnish with additional basil leaves, if desired.