adapted from Blackberry-Buttermilk Sherbet from page 129 of Pure Dessert by Alice Medrich
3 cups fresh blueberries, rinsed and drained
1 cup sugar
2 ¾ cups buttermilk
Pulse the berries and sugar in a food processor until they are pureed, but a few small chunks remain (alternatively, mash together by hand). Transfer blueberry mixture to medium bowl and stir in buttermilk. Chill the mixture in the refrigerator (the original recipe does not specify for how long; I left mine in for several hours, but an hour would probably be fine). For an extra-cold start, put the mixture in the freezer, stirring once or twice to prevent freezing (I did not do this). Freeze the mixture in your ice cream maker, according to the manufacturer’s instructions. Serve soft or transfer to an airtight container and freeze until hard enough to scoop. Best served within several days (I have been testing the boundaries on this, since the recipe makes a lot).