Preheat the oven to 350 degrees and line a baking tray with aluminum foil sprayed with cooking spray. Set aside.
With a large kitchen knife, slice the entire slab of Hawaiian rolls so that there are two even slabs.
Place the bottom slab of the rolls on the baking sheet.
Place 12 slices of the ham on the rolls. Then layer on the 12 slices of swiss cheese.
Add the last 12 slices of ham on top of the cheese and top it with the other half of the Hawaiian rolls slab.
Heat the butter in a microwave-safe container in 30-second intervals until it is completely melted.
ADD BUTTER TOPPING:
Add the dijon mustard, poppy seeds, Worcestershire sauce, and onion powder to the butter.
Whisk together until well incorporated.
Pour the butter mixture on top of the Hawaiian sweet rolls. You can also use a rubber food brush to brush the tops of the rolls with the butter mixture.
Let the rolls sit for 5 minutes.
Cover the rolls with additional aluminum foil.
Bake the sliders for 18 minutes.
After 18 minutes, remove the sliders from the oven and remove the top layer of aluminum foil covering the rolls.
Place the sliders back in the oven for an additional 5-6 minutes or until the tops are golden brown.
Remove the tray from the oven. Cut the sliders and serve warm.
SERVE: These sliders are best when served warm and should not sit out for longer than two hours. STORE: Once the ham and cheese sliders have cooled, place leftovers in an airtight container and place them in the refrigerator for 3-4 days.FREEZE: You can freeze these both before and after baking them. I like making a double batch of these sliders to freeze a second batch for later. Cover the pan in two layers of plastic wrap and two layers of foil to freeze. If you freeze the sliders before baking, bake them as per the recipe instructions once they have thawed.THAW: Thaw the sliders overnight in the refrigerator.REHEAT: Remove the plastic wrap, and cover the sliders with foil. Place the sliders in a 350 degree F oven for 10-15 minutes or until heated through.MAKE AHEAD: You can assemble the sliders, cover them and place them in the refrigerator for up to 24 hours before baking them.