In a saucepan, combine sour cream, cream cheese, onions and Worcestershire sauce; cook and stir over low heat until blended. Add cheese and ham; cook and stir until cheese is melted and ham is heated through. Cut off top of loaf; carefully hollow out top and bottom, leaving a 1/2-in. shell. Cut bread into cubes. Pour dip into shell; sprinkle with parsley if desired. Serve with bread cubes.