In A Large Soup Pot, heat the oil and cook the onions, stirring occasionally, until softened, about 10 minutes. Add the cabbage and continue to cook, stirring occasionally, about 20 minutes. Add the chicken broth, vinegar and ham hock. Cover and simmer the soup for 1 hour. Remove from heat, add salt and pepper as desired. Remove meat from ham hock and add back to soup. Serve with sour cream and chopped fresh dill.