What distinguishes a sherbet from a sorbet? Sherbets generally contain dairy, whereas a sorbet is a simple concoction of sugar, water and fruit (plus any additional flavorings desired). This unusual sherbet recipe combines blueberries and buttermilk, with nuances of lemon. The result? A super-smooth and creamy ice with a luscious plum color and a sweet-tangy taste; almost as rich as ice cream, but without most of the fat! Adding an egg white isn't uncommon for sherbets (egg whites are sometimes added to sorbets as well); it's a useful stabilizer for a densely textured sherbet whose base fruit is low in pectin or fiber. It works well here, but it's optional.
To make the simple syrup, combine the sugar and water in a small saucepan and bring to a boil over medium heat, stirring until the sugar is dissolved. Transfer the syrup to a clean container and let it cool. Covered, it will keep for up to 5 days in the refrigerator.
For the sherbet, place the blueberries and simple syrup in a saucepan and bring to a boil over medium-high heat. Turn off the heat, cover the pan, and let the mixture sit until cool. Transfer the mixture to a container, cover, and refrigerate until completely chilled.
Using a potato masher, roughly mash the fruit, leaving some of it whole, if you like. Add the buttermilk, lemon juice and zest, and whisk to combine.
Pour the sherbet base into an ice cream maker and freeze according to the manufacturer’s instructions. If you’re using the egg white, after 15 minutes of churning, lightly whisk the egg white with a fork to break it up, then add to the ice cream maker. Continue churning until the sherbet is fairly thick. Transfer the sherbet to a container, press a piece of plastic wrap or wax paper directly against the surface of the ice, and freeze until solid.
To serve, let the sherbet soften in the refrigerator for about 30 minutes before scooping.