Melt butter and mix in mustard, Worcestershire sauce and onion.
Cut the entire pack of rolls in half horizontally (keeping all top and bottom halves separately intact.)
In a 9x13 inch pan, place bottom half of rolls and cover with ham and cheese.
Cover ham and cheese stacks with top half of rolls.
Drizzle butter mixture over top of rolls, making sure onion is evenly distributed.
Bake uncovered at 350 degrees for 15-20 minutes and once finished separate for serving.