I have written an article on stress and sleep http://www.suite101.com/content/herbal-remedies-for-stress-and-sleep-a274726
that lists useful herbs for relaxing and promoting sleep such as peppermint, chamomile, mugwort and valerian. Aromatherapy essential oils such as lavender in an oil burner or a few drops in a warm bath can also help promote sleep. Discerning the why for the cause of insomnia is also helpful such as pain, stomach discomfort, anxiety, or as you suggested too much caffeine from the chocolate. Hope this is helpful.