1/2 lb. soft butter
3 tbsp. prepared mustard
1 1/2 tbsp. poppy seed
1 tsp. Worcestershire sauce
1 onion, grated
12 hamburger rolls
1 lb. chipped ham
12 slices Swiss cheese

Mix first 5 ingredients. Spread mixture on both sides of roll. Place ham and cheese on rolls. Wrap in foil. Heat 10 minutes at 400 degrees. May be made ahead and frozen or refrigerated.