Preheat the oven to 350 degrees. Cut the Hawaiian rolls in half and set aside. Place a slice of the ham and a slice of the Swiss onto the top of the bottom half of each roll. Place the tops on to each roll. Place the prepared sandwiches onto a large baking dish (you may need more than 1 depending on how many sliders you have).
Place the melted butter into a medium bowl. Add Worcestershire sauce, Dijon mustard, dried minced onion, and poppy seeds. Whisk together until smooth. Pour the sauce evenly over the tops of all the sandwiches in the baking dish. Allow sitting for 10 minutes or until the butter sets slightly.
Cover with foil, place into the oven and bake at 350 degrees for 10 minutes or until the cheese is melted. Uncover and bake for an additional 2 minutes until the tops are slightly browned and crisp. Serve warm.