Hawaiian Ham and Cheese Sliders

Ingredients (9)

• + cooking spray (such as Crisco®) add to pantry
• + ½ cup butter add to pantry
• ✓ 1 onion, minced
• + 3 tablespoons Dijon mustard add to pantry
• + 1 tablespoon poppy seeds add to pantry
• + 2 teaspoons Worcestershire sauce, or more to taste add to pantry
• + 1 (12 count) package Hawaiian sweet rolls, split, or more as needed add to pantry
• + 1 pound sliced deli ham, or more as needed add to pantry
• + 8 slices Swiss cheese, or more as needed add to pantry