Place tart cherries with can liquid, frozen Bing cherries, half-and-half, and chocolate syrup in blender. Cover and process on HIGH until very smooth. Taste, add vanilla extract to cherry mixture, and blend until smooth. Stop and scrape sides of blender to mix well. Freeze cherry mixture in ice cream maker, according to manufacturer's instructions.
Remove from freezer and scoop into serving dishes. Garnish each serving with a mint sprig and cherry, if desired. For best flavor, let stand 15 minutes at room temperature before serving.