Preheat the oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish.

Without separating the rolls, slice the entire batch of Hawaiian rolls horizontally to create a top and bottom layer. Place the bottom half in the prepared baking dish.

Layer the ham evenly over the bottom rolls, then arrange the halved Swiss cheese slices on top. Place the top half of the rolls over the filling.

In a small bowl, whisk together the melted butter, Dijon mustard, poppy seeds, minced onion, Worcestershire sauce, garlic powder, salt, and black pepper.

Pour the butter mixture evenly over the tops of the sliders, using a spoon or brush to spread it into the crevices.

Cover the dish with foil and bake for 15 minutes.

Remove the foil and bake for an additional 5 to 10 minutes, until the tops are golden and the cheese is melted.

Let the sliders rest for 2 to 3 minutes before slicing and serving warm.