Preheat oven to 350 degrees

Melt butter over medium heat and saute the onions in the butter for 1-2 minutes.

Then add the mustard, worcestershire, and poppy seeds. Simmer for for about 5 minutes, until the onions are soft.

Cut the entire pack of rolls in half, horizontally…keeping all the top and bottom halves separately in tact.

Spray a 9×13 casserole dish with non-stick spray, place bottom half of rolls, and spoon 1/2 of the onion mixture over the rolls.

Add a slice of ham and sprinkle swiss cheese over each roll.

Cover with the top half of rolls.

Spread the remaining onion mixture and any extra cheese over the top.

Bake covered for 15-20 minutes, and once finished, separate for serving.