1/2 lb. butter
3 tbsp. mustard
3 tbsp. poppy seed
1 med. onion, chopped
1 tsp. Worcestershire sauce

Split Pepperidge Farm party rolls. Spread top and bottom of balls. Place on rolls:

1 lb. baked ham
1/2 lb. (or more) Swiss cheese, shredded or sliced

Bake until cheese is melted.