Pour 1 cup cream mixture into sugar mixture, and whisk until cornstarch is dissolved. Add remaining cream mixture, and whisk until smooth. Bring to a boil, whisking constantly, and cook until thick, about 5 minutes. Reduce heat to low, and add chocolate. Whisk until chocolate melts, about 1 minute.Remove from heat. Add mint extract and butter, and whisk until butter melts. Quickly divide pudding, whisking as you work to prevent sides from setting up, among eight 4-ounce glasses or glass flowerpot votive candle holders (candle4less.com
), leaving about 1/2 inch of space at the top of each. Refrigerate until set, about 1 1/2 hours.