1. In a food processor, puree Gouda, cream cheese, mayonnaise, mustard, ham, olives, onion powder and Worcestershire sauce until smooth. Taste and season with pepper.
2. Using a small knife, carefully spread filling into celery pieces (alternatively, spoon into a large ziplock bag, seal bag and snip off a corner, or use a pastry bag with a plain tip, to pipe filling into celery). Sprinkle with chives and serve.