Preheat oven to 400°.
On a rimmed baking sheet or casserole dish, place the bottom half of dinner rolls and top with 1 1/2 slices of ham and the cheese.
Spread about 1 teaspoon of mayonnaise on each TOP-half of the outside TOP roll and place on top of the ham and cheese. (this is helping to create the delicious topping that coats these sliders' rolls). Place the rolls snugly together in your casserole dish.
In a separate small bowl combine the mustard, melted butter, onion powder, Worcestershire sauce, poppy seeds, and brown sugar. Mix until well combined and evenly pour or spread over the assembled rolls.
Cover with foil and refrigerate until ready to bake.
Bake covered with foil for 10 minutes, remove the foil and bake for an additional 5-10 minutes or until the tops are browned, and cheese is nice and melted.