Use a serrated knife to cut the rolls in half. You can make this extra easy by not separating the rolls—just slice the entire sheet of rolls in half horizontally.
Cut the cheese slices into quarters.
Place the bottom of the rolls into TWO 13x9 inch pans. Top each roll with a slice of ham (folded to fit). Then top that with two pieces of the sliced cheese. Place the tops of the rolls on top of the sandwiches.
Stir together the melted butter, mustard, worcestershire sauce, and onion powder. Pour the mixture evenly over the sandwiches (some butter will pool at the bottom and that is ok!). Sprinkle evenly with the poppy seeds.
Cover the pans with foil and bake for 20 minutes. Uncover and bake for an additional 5 minutes, or until lightly golden brown on top.
Serve immediately.
Notes
Give the butter/Dijon mixture a good stir just before pouring it onto the sliders. Otherwise the Dijon won't be evenly distributed among the sandwiches. Store leftovers in the refrigerator. Reheat in a 350°F oven, covered with foil, for 5–8 minutes or until warmed through. How much to make? In my experience, people will eat anywhere from 2–4 sliders each (2 as an appetizer, 3–4 as a main course). More customization ideas:
Add two slices of ham and more cheese to make an extra hearty sandwich.
Swap turkey or roast beef for the ham. I've even made these with leftover prime rib!
Swap your favorite variety of sliced cheese (Colby Jack, cheddar, American, provolone, pepper jack, Muenster, etc.) in place of the Swiss cheese.
Use onion flakes in place of the onion powder.
Sub soy sauce + a pinch of sugar for the worcestershire sauce.
Use leftover ham from the holidays in place of deli ham.
Meat and cheese combo ideas: roast beef and cheddar; turkey and Havarti; ham and Muenster; ham, turkey, and pepper jack, etc. Use your favorite combo!