Preheat the grill to 350°F. In a small bowl, combine 1/2 cup melted butter with 1/2 tablespoon Dijon mustard, 1/2 tablespoon Worcestershire Sauce, 1 1/2 teaspoons poppy seeds, and 1 teaspoon dried minced onion. Whisk to combine.
Slice the tops off the rolls and carefully set them aside until ready to use. Lay the bottom halves of the rolls in a 13×9 casserole dish.
Layer cheese slices on the rolls and layer ham slices on top of the cheese. I lay one slice of ham on each bun.
Carefully place the bun lids on top of the ham and pour on the buttery mustard glaze.
Bake on the grill, indirect method, preheated to 350°F for 15-20 minutes until the cheese is nicely melted and the sliders are warmed through.