Mix Cheddar cheese, cream cheese, blue cheese, butter, onion, and Worcestershire sauce together in a bowl using an electric mixer or in a food processor until thoroughly blended. Stir in finely chopped filberts. Divide mixture into 2 balls using wet hands. Wrap balls in waxed paper and refrigerate until cool and firm, about 1 hour. Smooth and shape; roll firmly in chopped filberts. Wrap in plastic wrap and refrigerate until ready to serve, at least 1 hour. Garnish each cheese ball with 1 cherry half and parsley 1 hour before serving.