Heat your oven to 350°F and grease a 9x13 inch baking pan using cooking spray.
In a bowl, whisk together melted butter, brown sugar, Dijon mustard, Worcestershire sauce, poppy seeds, and dried minced onion until combined.
Slice the rolls horizontally and layer the bottom halves evenly in the baking dish.
Spread half of the ham slices over the bottom layer of rolls.
Add a layer of Swiss cheese on top of the ham, then add the remaining ham slices.
Place the top halves of the rolls back on top to form complete sandwiches.
Pour the butter mixture evenly over the assembled sliders.
Cover the pan tightly with foil and bake for 15 minutes.
After 15 minutes, remove the foil and continue baking for another 10 minutes until the tops are golden and the cheese is melted.
Take out of the oven, slice the sliders apart, and serve warm immediately.