Garnish:
In a small bowl, stir together mayonnaise, grated cheese, ANGOSTURA® aromatic bitters, mustard (if using), and cayenne pepper.
In a medium bowl, combine egg yolks, celery and onion. Mash with a fork until crumbly. Stir in mayonnaise mixture. Season with salt to taste, and add more cayenne pepper if desired.
Spoon into egg-white halves. Sprinkle with paprika if desired. Serve immediately or refrigerate until ready to serve.