Preheat oven to 350 Degrees F
Without separating them individually, use a long serrated knife (or electric knife) to slice the rolls in half horizontally, creating a layer of tops and a layer of bottoms.
Whisk together the melted butter, mustard, poppy seeds, Worcestershire sauce, onion, salt, and pepper.
Place the bottom "sheet" of the rolls into a baking dish. (We used a 9x13 dish) Layer on half of the ham, followed with the cheese slices. Follow with a layer of the remaining ham, and top with the top layer of rolls.
Next, brush on or use a spoon to cover the rolls with the butter mixture.
Cover the baking dish tightly with aluminum foil and bake for 15 minutes to melt the cheese. Next, remove the foil and bake uncovered a few minutes more until you've reached the desired amount of brownness (approximately 5-8 minutes more but watch closely and adjust as needed- baking times will vary).
Using a knife, separate the sliders and serve warm. Enjoy!