Melt butter in a small skillet. Once melted add onions.
When onions begin to soften add mustard, Worcestershire sauce, and poppy seeds into onions and butter. Simmer for two to three minutes.
Remove rolls from package, keeping them all connected and cut the rolls in half lengthwise. Place the bottoms in a 13 x 9 pan lined with aluminum foil.
Spread ½ of the butter and onion mixture across rolls bottoms follow by the ham and then the cheese.
Top with the rolls tops and spread the remaining butter and onion mixture over the top of the rolls. Cover with aluminum.
Bake covered with foil for 20 minutes on 350 or till all the cheese is melted.
*You can freeze and refrigerate these sandwiches. If frozen cook in a 50 degree cooler over for 15-20 minutes longer. Recommended to thaw in fridge before baking though. Sandwiches that come out of the fridge to oven may take 30 minutes on 350.