Combine all ingredients but pears in a large saucepan. Bring mixture to a boil and cook 5 minutes. Add pears, lower heat, and cook 20 to 30 minutes, until pears are tender. If necessary, turn pears very gently by rotating stems with your fingertips so they cook evenly. Remove pears to a bowl, bring poaching liquid to a rapid boil, and reduce by half, about 10 minutes.
Pour syrup over pears and refrigerate, covered, at least 6 hours, preferably overnight. Serve.