1 pound fresh black cherries, pitted, or two 10-ounce bags frozen pitted
black cherries, thawed
1 1/4 cups sugar
1/4 cup fresh lemon juice
3 whole star anise
1/2 vanilla bean, split and scraped
16 green-tea bags
Mint sprigs, for serving
Bring the water to a boil in a large saucepan. Add the black cherries, sugar, lemon juice, star anise and the vanilla bean with its seeds. Simmer the cherries over low heat for 15 minutes, crushing them against the side of the pan with a wooden spoon. Remove the cherries from the heat, cover and let stand for 1 hour.
Strain the cherry juice through a fine sieve into a clean saucepan, pressing on the solids. Discard the solids. Bring the cherry juice to a boil over moderate heat. Remove from the heat, add the tea bags and let steep for 5 minutes. Discard the tea bags and let cool to room temperature. Transfer the cherry tea to a large pitcher and refrigerate until chilled or for up to 2 days. Serve the tea over ice, garnished with mint sprigs.