The traditional root beer float reinvented. A quart of ice cream is whirled with sour cherries until frothy and then capped with shards of frozen soda.
Pour root beer into a baking pan and freeze, uncovered, until firm, about 2 1/2 hours. Using a fork, scrape into small shards. Cover, and freeze until ready to use.
Puree ice cream and reserved cherry juice in a blender until smooth. Add cherries, and pulse until combined but still chunky. Divide among 6 to 8 glasses, and top each with 2 tablespoons root beer granita.
Bottled sour cherries are available online or at specialty food stores.