Layer each roll with a slice of ham and a half slice of cheddar cheese.
In a microwavable bowl, cover and heat butter for about 30 seconds or until melted. Stir in Dijon mustard, Worcestershire sauce, and onion powder.
Add top layer of rolls and brush with mustard-butter mixture.
Loosely cover with foil and bake at 350˚ for about 15 minutes. Remove foil and bake an additional 5 minutes or until cheese is melted and tops of buns are golden brown.