Wash, drain, and chop the greens, set aside. Place the ham hock and skin in a large kettle, and add about 3 quarts cold water to cover. Bring to a boil over high heat. Simmer over moderate heat for 30 minutes. Add the greens and sugar and simmer for 2 hours. Drain the “likker” and serve it with the greens and spooned over corn bread.