Preheat the oven to 350°F. Line a large baking dish with aluminum foil. Spray with cooking spray and set it aside.
Slice the rolls in half. Place the bottom slab of rolls in the prepared pan.
Add the sliced ham on the rolls. Then add a layer of cheese.
Add the top slab of the rolls; set aside.
In a medium sized microwave safe bowl, add the butter and heat it on high for about one minute until melted.
Add the mustard, poppy seeds, onion, Worcestershire sauce, salt, and pepper. Whisk until combined.
Slowly pour the butter mixture over the rolls and use a spatula to spread the mixture all over the tops. Some of the butter will pool at the bottom of the rolls.
Cover the pan with foil and let the rolls rest at room temp for 5 to 10 minutes.
Bake covered for about 20 minutes or until the cheese has melted.
Uncover the pan and bake for 3 to 5 minutes until golden brown. Be sure to watch the rolls carefully so they don’t burn.
Slice the rolls into individual sliders and serve while they’re still warm.