1. Preheat the oven to 350°F and lightly grease a 9×13-inch baking dish.

2. In a small bowl, whisk together the melted butter, Dijon mustard, Worcestershire sauce, onion powder, and kosher salt until smooth.

3. Without separating the rolls, slice the entire pack of rolls in half horizontally using a serrated knife. Place the bottom half into the prepared baking dish.

4. Layer 6 slices of Swiss cheese evenly over the rolls. Add the turkey slices on top, folding them slightly to fit evenly across the rolls.

5. Place the remaining 6 slices of Swiss cheese over the turkey, then set the top half of the rolls in place.

6. Brush the butter mixture generously over the tops of the rolls. Sprinkle the poppy seeds evenly across the top.

7. Cover the dish tightly with aluminum foil and bake for 20 minutes, or until the cheese is fully melted and the sliders are heated through.

8. Remove the foil and continue baking for 7 to 8 minutes, until the tops are lightly golden.

9. Let cool for a few minutes, then slice into individual sliders and serve warm.